Email List Decay Calculator: How Many Customer Emails Still Work?

Email list decay is the share of addresses on a list that stop reaching a person each year. ZeroBounce's study of 2025 data says at least 23 percent of a list decays within one year (vendor study, read November 5, 2026). That is a vendor figure for mixed lists, not your list, so check yours before you mail.

If you already know your list size and age, jump to the calculator. Once you know how many addresses still work, what email marketing costs in Kansas City covers what sending to them costs once the list is clean, with Email Marketing KC's price table on the page.

Key facts

• At least 23 percent of an email list decays within one year, 2025 data, vendor study (ZeroBounce).
• HubSpot's 22.5 percent a year traces to an undated footnote citing 2.1 percent a month for B2B data (HubSpot).
• U.S. job quits compound to 21.21 percent a year, October 2025 to September 2026 (BLS JOLTS, compounded by me).
• ContactLint checks 250 addresses a month free, then 5,000 for $9 (ContactLint pricing, read November 5, 2026; my business).
• 0 of 15 ranking decay pages fully explain how their figure was measured, 1 partly (my audit, 2026-11-05).

Email list decay calculator

Nothing you type leaves your browser, and the page asks for no email. Use your own numbers wherever you have them: list size, age, the hard bounce rate on your last send, repeat orders and order value.

What it does not do: it claims no lift from cleaning, it says nothing about what any email tool will do with your bounces, and its four rates are published benchmarks read on November 5, 2026, not measurements of your list. For the cost of the send itself, use the marketing cost calculator, which has an email line.

What email list decay is, and what it is not

Email list decay is the share of addresses that stop reaching a person. The causes are job changes, closed businesses, abandoned inboxes and typos at signup. The address is dead or wrong, and no subject line fixes that.

Three things are not decay. An unsubscribe is a working address whose owner chose to leave. Low engagement is a working address whose owner does not open. A spam complaint is a working address whose owner reported you, and that rate is the one Google and Yahoo tell senders to keep under 0.30 percent.

This matters for your math. When I typed 10,000 addresses, 100 unsubscribes and 50 bounces a month into emailcalculator.com on November 5, 2026, it added the two and called the sum decay: 150 a month, 1,800 a year. The calculator above counts only addresses that cannot receive mail.

Our data: what 15 ranking decay pages and 3 working calculators show

I ran this on November 5, 2026: Google US page one through Serper for two queries, "email list decay calculator" and "how fast does an email list decay per year percent", every organic result kept, and the 17 unique pages loaded in headless Chrome by script, of which 15 were readable and two returned HTTP 403. A script checked the text and form fields, and I checked source, year, method, working calculator, compounding, small business framing and AI search advice by hand on the saved text. I also typed numbers into the three working calculators in the top four results and recorded what came back. Counts are for these pages only and are not a market estimate.

The files: page audit, decay scenarios, BLS JOLTS 12-month series and cost to check.

Three examples from the file. HubSpot's page states 22.5 percent a year and rests it on a footnote crediting MarketingSherpa at 2.1 percent a month for B2B data, with no report title, year or link, and three of the eight pages that name a source point back to HubSpot. emailcalculator.com's yearly loss is the monthly loss times 12: 150 times 12 is 1,800, while compounding 1.5 percent a month over 12 months (0.985 to the twelfth power, about 0.834) would leave about 8,341 of 10,000, not 8,200. Only 2 of 15 pages give a year or data period for their figure.

The honest takeaway: the numbers are everywhere and the methods are nowhere. Treat every published rate, including the four in my calculator, as a benchmark to overwrite with your own bounce data.

What published decay rates say, side by side

Five sources, each with what it measures and where it is weak. None of them measured your list.

Reading it: reachable is list size times (1 minus the rate) to the power of years, so at two years the four benchmarks leave 451 to 621 of 1,000 addresses reachable, a 170-address spread, and none of them measured your list. I found no sourced consumer-only decay rate on any page I read, so the consumer default is ZeroBounce's mixed-list figure, marked editable.

How to use this calculator, step by step

1. Count the addresses and the age of the list

Export the list from your email tool, point-of-sale or booking system as a CSV with the email column and, if you have it, the date each address was collected. Age is years since the address was collected or last verified; if the list was built over several years, split it into batches by year or use the middle year.

Time: 10 to 20 minutes (my estimate).

Done when: you have one list size and one age in years, or several batches that each have both.

2. Pick a published rate, or type your own, and read all four

Choose consumers or businesses. The calculator prefills the rate from four published benchmarks (ZeroBounce 23 percent, HubSpot 22.5, BLS quits 21.21, BLS total separations 32.87), lets you overwrite it, and runs reachable = list size x (1 minus rate) to the power of years under all four at once.

Press Try a sample to see the worked example: 1,000 addresses, two years, 23 percent, a 3 percent bounce, 0.5 repeat orders a year and a $45 order give 593 reachable, 407 stale (40.7 percent), a gap of about 204 orders and $9,158 a year, and $9 to check.

Time: 2 minutes (my estimate).

Done when: you have a reachable count under each of the four rates and can see the spread between the lowest and the highest.

3. Read the hard bounce rate from your last send and use the cross-check

Open the report for your last campaign in your email tool. Bounce rate is hard bounces divided by addresses sent, times 100; on the sample, 3 percent of 1,000 is 30 addresses. The calculator multiplies your rate by the list size to get a floor of stale addresses.

If the floor is above the benchmark's stale count, your list is staler than the benchmark. If it is below, the difference is addresses that are dead but did not bounce (catch-all domains, or addresses you never mailed).

Time: 5 minutes (my estimate).

Done when: you have one number for hard bounces on one send, and the calculator shows that floor beside the benchmark stale count.

4. Enter repeat orders per customer per year and average order value

Both come from your own history: orders in the last 12 months divided by the customers who placed them, and total sales divided by orders. The gap is stale addresses times repeat orders times order value, and it is revenue attached to addresses that cannot receive an email. It is not an email lift, and the calculator never claims one.

Time: 10 minutes with your POS report open (my estimate).

Done when: the gap is on the screen and you can say where each of the two inputs came from.

5. Check the list before you send, then keep a dated record

Run the addresses through a check before the send. ContactLint (my business) gives 250 free checks a month with no card and then 5,000 for $9; it flags bad syntax, dead domains, disposable and role addresses and typos, but it never opens an SMTP connection to the mailbox. For dead mailboxes on live domains, use a mailbox verifier.

Send to the clean part, then write down the date, list size, reachable count, verdicts and the hard bounce rate on that send.

Time: 30 minutes to an hour (my estimate).

Done when: every address has a verdict, the typos are fixed, and a dated note records the size, the reachable count and the bounce rate on the next send.

Why lists go stale

Job changes

In September 2026, BLS JOLTS (released November 3, 2026, preliminary) counted 3.4 million quits, a rate of 2.1 percent, and 5.3 million total separations, a rate of 3.3 percent; layoffs and discharges were 1.6 million, 1.0 percent. Averaged over October 2025 to September 2026 and compounded over 12 months, the mean monthly rates come to 21.21 percent a year for quits, 32.87 percent for total separations and 12.25 percent for layoffs and discharges (my arithmetic; the 36 monthly values are in the JOLTS CSV above).

These count jobs across all employees, not email addresses. A person who quits keeps a personal address and loses the work one, so the rates point at work addresses only.

Closed businesses

The Census Bureau's Business Dynamics Statistics count 699,980 establishment exits in 2023 out of 7,494,983, an exit rate of 9.396 percent (9.512 in 2022, 10.110 in 2021). An establishment is a location, so a chain closing one store counts as an exit while the firm lives on.

Young locations leave faster. BLS Business Employment Dynamics followed private-sector locations born in March 2013: 79.6 percent were still operating after one year, 68.9 after two, 50.6 after five and 34.7 after ten. Retail did a little better (84.2, 75.7, 58.3, 41.7) and accommodation and food services a little worse (82.5, 72.5, 55.3, 38.2). 100 minus 79.6 leaves 20.4 percent of new locations gone in their first year, against 9.396 percent for locations of all ages.

The calculator shows the 9.396 percent line for business lists as a separate cross-check and never adds it to job turnover, because a closure already shows up in the BLS separations.

Abandoned inboxes and typos

I found no sourced rate for consumer addresses that go quiet, so the calculator invents none. The nearest signals come from verifiers, and they describe the lists people send to verifiers, not yours. ZeroBounce says only 62 percent of the addresses submitted to it in 2025 were valid.

BounceZero re-checked 826K addresses between February and July 2026 and found 74.3 percent of once-valid addresses still valid within 30 days, 44.9 percent at 31 to 90 days and 19.2 percent after more than 90 days, then said its own figures are probably pessimistic because re-checks are self-selected and prospecting lists dominate. Typos are the one cause a check can fix: a misspelled provider domain comes back from ContactLint with a suggested correction.

Catch-all and role addresses

ZeroBounce reports that more than 9 percent of the emails it checked in 2025 were catch-all. A catch-all domain accepts mail for any name, so no checker, DNS or SMTP, can tell a live mailbox from a dead one there. A role address such as info@ or admin@ reaches a desk, not a person, and the person at the desk changes; ContactLint flags role addresses so you can decide.

What bounces mean, and what the rules say

A hard bounce is an address the receiving server rejects. A soft bounce is a temporary failure. Mailchimp's help page says hard bounced addresses are in most cases cleaned from your audience automatically and immediately, and that it allows 7 soft bounces for an address with no subscriber activity and up to 15 for contacts with previous activity before converting a soft bounce into a hard bounce.

Neither Mailchimp nor Klaviyo prints a bounce rate limit on the pages I read (Klaviyo's page updated July 7, 2025). Klaviyo says repeated problems with hard bounces, unsubscribes or spam complaints can lead to account disablement, with no number attached. Any page that tells you a tool suspends at 2 or 5 percent is quoting a figure the vendor has not published.

The 0.30 percent you see in sender rules is a spam complaint rate, not a bounce rate. Google's sender guidelines say: "Keep spam rates reported in Postmaster Tools below 0.10% and avoid ever reaching a spam rate of 0.30% or higher." On bounces they say: "If messages start bouncing or start being deferred, reduce the sending volume until the SMTP error rate decreases." and "Automatically unsubscribe recipients who have multiple bounced messages."

Yahoo's sender requirements say "Keep your spam rate below 0.3%" and "Remove invalid recipients from your list promptly." and ask senders to honor unsubscribes within 2 days.

The law sits above the tools. The FTC's CAN-SPAM guide says each separate email in violation is subject to penalties of up to $53,088, and that you must honor an opt-out request within 10 business days. Not legal advice; read the guide.

What a clean list can and cannot bring back

A check fixes the typos it can suggest a correction for and removes addresses on dead domains. It does nothing for a person who changed jobs, closed the shop or abandoned the inbox. So a clean list restores the chance to reach some people; it earns nothing by itself.

The one repeat-customer figure with a published method that I use is Square's. Its 2026 Local Economy Report (vendor study, March 18, 2026) defines a regular as a customer who visits a business at least four times a year and says "Regular customers generate 6X more annual revenue than one-time visitors nationally." That compares two kinds of customers you already have. It does not say an email turns a one-time visitor into a regular, and I will not say it either.

The line you will see elsewhere, that a 5 percent rise in retention lifts profit by 25 to 95 percent, traces to a Bain brief that says: "In financial services, for example, a 5% increase in customer retention produces more than a 25% increase in profit." One industry, no 95, no sample, no method. Leave it out of your math.

What the calculator's dollar gap means: stale addresses times your repeat orders per customer per year times your average order value. On the sample, 407 x 0.5 x $45 = $9,157.50, which the tool rounds to $9,158. That is revenue attached to addresses that cannot receive your email, not revenue an email would create.

Mistakes that cost the most

1. Mailing a two-year-old list without checking it

Take the sample: 1,000 addresses collected two years ago at ZeroBounce's 23 percent a year. 1,000 x 0.77 x 0.77 = 592.9, so 593 reachable and 407 stale. With the sample's 0.5 repeat orders a customer a year and $45 average order, 407 x 0.5 x $45 = $9,157.50 a year attached to addresses that cannot get the email. That is example arithmetic on the sample's inputs, not a result, and not what cleaning would earn you.

Fix: check first, send only to the reachable part, and let the hard bounces on that send tell you whether the benchmark was too kind.

2. Trusting one number

The same 1,000 addresses at two years give 621 reachable under the BLS quits rate (21.21 percent) and 451 under BLS total separations (32.87 percent). 621 minus 451 is 170 addresses, 17 percent of the list, between two government rates that describe the same workers. Any page that hands you one number is hiding that spread.

Fix: read the table under all four rates, then overwrite the rate with the hard bounce data from your own last send.

3. Buying a big verification pack for a small list

ContactLint's cheapest cover is $9 for a list of 1,000 to 5,250 addresses (250 free, then one 5,000-check pack), $18 at 10,000, $35 for 25,000 and $99 for 100,000, read November 5, 2026. For a list of 1,000, paying for the 25,000 pack costs $35 minus $9, or $26 more than you need. Unused credits are refundable within 14 days, so the mistake is fixable, but only if you notice.

Fix: price the cover first; the calculator prints it for your list size.

Do nothing vs a DNS and syntax check vs a mailbox verifier vs a small test send

I own ContactLint, the DNS and syntax check in row two, and Email Marketing KC, which sells list care. Time and effort below are my estimates.

My pick for most local shops: for a list under a few thousand addresses, run ContactLint's free 250 checks on a slice or a mailbox verifier on a sample, then decide. A mailbox verifier catches more than ContactLint does, because it asks the mailbox; use ContactLint when the problem is typos, fake and dead domains, and when $9 is the budget. Never treat the DNS check as the whole answer.

How I weighted the options

Catch rate leads because every other number on this page depends on how many addresses are real, and the cheapest check in the world is worth nothing if it leaves the dead mailboxes in.

I own ContactLint and Email Marketing KC, so I have a stake in two of the options on this page. I get nothing from ZeroBounce, Kickbox, Emailable, NeverBounce, Mailchimp, Klaviyo or any other vendor named here. The calculator is free, asks for no email and sends nothing to me. Nothing on this page is legal or financial advice. More about me is on the about page.

Verdicts, by type of list

Who this is not for

A list your email tool already mails every month. If the list is opted in, sent to monthly and cleaned of hard bounces by the tool, the tool's bounce report is a measurement and this calculator is a benchmark. Read the report instead.

A purchased or scraped list. Do not mail it at all. CAN-SPAM's rules apply (penalties of up to $53,088 per separate email in violation, and opted-out addresses cannot be sold or transferred, even as a mailing list), your email tool's own rules apply, and BounceZero's re-checks, which over-weight prospecting lists, found only 19.2 percent of once-valid addresses still valid after more than 90 days. Not legal advice.

A list of more than a few hundred thousand addresses. Use a full verification vendor, ask for a sample result on a slice before you pay for the whole list, and read its data policy on where the addresses go.

How a page like this gets found with AI

Of the 15 ranking pages I read on November 5, 2026, 0 say anything about getting found in AI search and 0 explain how their decay number was measured beyond one partial. Those are the same gap. An assistant answering "how fast does an email list decay" needs a number with a source, a date and a method, and the number most pages repeat, 22.5 percent, traces to one undated footnote.

So this page puts every number in plain HTML text with its source and date, carries a dated read line and a method sentence, publishes a clean Markdown copy, and allows the AI search crawlers in robots.txt (1 of 15 ranking pages blocks them). Google and OpenAI both say there is nothing special to add:

"There are no additional requirements to appear in AI Overviews or AI Mode, nor other special optimizations necessary."

Google Search Central, AI features documentation, read October 31, 2026

"Sites that are opted out of OAI-SearchBot will not be shown in ChatGPT search answers"

OpenAI, bots documentation, read October 31, 2026

Do the same for your shop: publish your prices and your plain answers as dated HTML text that a customer and an assistant can both read. That improves the chance ChatGPT, Claude, Perplexity, Gemini or Google AI Overviews can quote you; nobody can promise they will. My guide to getting a Kansas City business into ChatGPT and Gemini walks through it, and the AI visibility scorecard checks your site.

How I put this together

On November 5, 2026 I pulled Google's US page one for "email list decay calculator" and read today's top three in headless Chrome.

1. emailcalculator.com's email list decay calculator (470 words, no date shown). Does well: a working tool with three inputs and clear tiles for monthly loss, yearly loss and the new subscribers needed to hold size. Misses: "Research shows" names no research; its yearly figure is the monthly loss times 12 on a list that never shrinks; unsubscribes and soft bounces count as decay; no list age, no order value, no cost to check.
2. mailtester.com's B2B email list decay rate per year (4,275 words, dated August 28, 2026). Does well: long, dated, answer-first sections, a verdict table for valid, invalid, catch-all and risky addresses, and a bounce-based way to measure decay written out in prose. Misses: credits "22% annually" to "data from marketing operations teams, CRM usage patterns, and outbound sales benchmarks" with no link or year; no calculator; consumer lists, small shops and revenue are absent.
3. mailthentic.com's list decay calculator (313 words, no date shown). Does well: compounds a shrinking list correctly, three clean result tiles, no signup. Misses: "Industry benchmarks put monthly decay around 2 to 3%" names no benchmark; the rate must be typed as a monthly percent; no bounce, age, list-type or order input; no cost to check shown.

This page adds: four named and dated benchmarks side by side, a backward look at a list you already have, a bounce cross-check, the dollar gap, the cost to check at your list size, a four-way comparison of ways to check with my stake disclosed, what the rules say in the vendors' own words, and a section on getting found with AI, which 0 of the 15 ranking pages touch. All my guides live at the articles index.

Run the calculator above with your list size and age. If it shows hundreds of stale addresses, check the list: ContactLint (my business) gives 250 free checks a month and then 5,000 for $9, and a mailbox verifier catches more for more. If the reachable part is worth mailing, read what email marketing costs in Kansas City, see Email Marketing KC's published prices (my business; read November 5, 2026: a 4-email pilot at $600 to $1,200 with a written floor based on list size, an email review at $747, setup at $2,800 that includes cleaning the list, monthly emails at $1,850 a month and weekly emails at $3,900 a month, both month to month, and you keep paying for your own email tool), or email [email protected] with your list size and age and I will tell you honestly whether a check or a send comes first. Next read: what email marketing costs in Kansas City. More calculators are on the tools page.