Free tool
Email bounce cost calculator
Bounces are not free. You pay to send to an address that was never going to arrive, and you pay again in sender reputation when a mailbox provider notices how many of your recipients do not exist. Set the four figures below to match how you send, and see the first cost in money.
Bounce cost calculator
Your list
Set these to match how you send today.
What you could keep in the first year
Up to$733
At best, verifying could pay for itself after 3 sends to the list.
- Addresses likely to bounce10,000 × 8%
- 800
- Spent sending to them each year4 emails a month × 12 × $0.020
- $768
- Verifying the list onceOne 10,000-credit pack, the cheapest way to buy credits for 10,000 addresses
- −$35
100 free verifications, no credit card required
How this estimate worksA ceiling built from your four numbers and published prices. Real savings will be lower.
A ceiling, not a forecast
It assumes every address that would bounce is found and removed before you send. Verification cannot promise that: some addresses can only be marked risky or unknown, and an address that checks out can still bounce later, so real savings will be lower.
Priced as what you can buy
Checking the list costs the cheapest way to buy enough credits for it once, at list prices in US dollars before tax: credit packs, one month of a plan, or a month of a plan with packs on top. Never a per-address rate, which prices a bundle nobody sells. It leaves out the 100 free credits a new account starts with. Packs need no subscription and can be bought on any plan, including Free, where buying any pack also raises one bulk job from 100 to 1,000 addresses, so a longer list goes in several. A plan is a monthly subscription you can cancel before it renews. The pricing page lists every pack and plan.
Hard bounces only
A soft bounce (a full mailbox, greylisting, a server having a bad day) is a temporary failure to retry, not an address verification removes. Enter your total bounce rate and every figure here comes out too high.
Every send, for a year
It charges today’s bad addresses to every send for twelve months. If you suppress an address after its first hard bounce, you pay much of this once rather than every campaign. Lists also go stale continuously, so neither figure is the whole story.
Sending costs only
Only the cost of sending is counted. Effects on sender reputation and inbox placement are not given a dollar value.
The arithmetic
Exactly what it works out
Four multiplications and a subtraction, with nothing hidden.
The rate it asks for is your hard bounce rate. A soft bounce (a full mailbox, greylisting, a receiving server having a bad day) is a temporary failure you retry, not an address a one-off verification takes off the list, and folding those in inflates every figure below.
Addresses that hard bounce
list size × hard bounce rate
Wasted per send
bouncing addresses × cost to send one email
Wasted per year
wasted per send × sends a month × 12
Cost to check the list once
the cheapest mix of credit packs and one month of a plan that buys a credit for every address
First-year difference
wasted per year − cost to check the list
Sends to break even
cost to check the list ÷ wasted per send, rounded up
What it leaves out, on purpose
A catch rate. No verifier finds every bad address on a list, and Kawaa publishes no accuracy figure it has not benchmarked. So the saving is shown as a ceiling, the most a perfect clean could return, rather than a forecast.
A dollar value on reputation. Reputation, deliverability and recovered revenue are real, but none of them is a number anyone can honestly multiply your inputs by.
Suppression. The annual figure charges today’s bad addresses to every send of the year. If you suppress an address after its first hard bounce (which you should, and which the deliverability guide on this site says too), you pay for that set roughly once, and the annual figure is far too high.
List decay. Pulling the other way, lists go stale continuously: addresses that are fine today bounce in six months.
Read it as a figure that bounds the problem rather than measures it.
Beyond the postage
The cost that is not on the invoice
A hard bounce tells the receiving mailbox provider something about you: that the address you sent to was invalid or long stale by the time you used it, which a mailbox closed since the last check can be too. Do it at scale and the provider starts treating the rest of your mail with suspicion: more of it lands in spam, and the addresses that do exist stop seeing you. That is the part the calculator above cannot price, and it is usually the larger number.
It is also why a list that has been sitting unused is riskier than a large one that is sent to weekly. Addresses decay on their own: people change jobs, mailboxes are closed, and providers recycle abandoned ones into spam traps. How much of a given list has gone that way is not something anyone can tell you from its age, which is the argument for measuring your own rather than taking a figure off a blog.
The practical reading: how to reduce your bounce rate and the deliverability audit checklist. To see what a verification actually returns, the free email verifier runs one against the live API without an account. Verifying a sample of your own list shows what share of it comes back invalid or risky: a better input to the figures above than a guess, though not the same thing as a measured bounce rate.
Questions
About this calculator
Where do the numbers come from?
Why does it say "up to" rather than a figure?
How is the cost of checking the list worked out?
What does "sends to break even" mean?
Is my list data sent anywhere?
Check the list, not the estimate
A free account includes 100 verification credits and the CSV upload: enough to sample your list and see what share of it comes back invalid or risky.
No credit card required