Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Subscriber lifetime value
$22.00
Expected subscriber lifespan
28.6
Max sustainable cost per new subscriber
$7.33
Contribution value per subscriber per year
$9.24
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How to use this
- 1Enter monthly revenue per active subscriber ($).
- 2Enter monthly list churn (unsub + inactive) (%).
- 3Enter contribution margin on that revenue (%).
- 4Enter target ltv:cac ratio for signups.
- 5Read your subscriber lifetime value on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
A monthly revenue-per-subscriber number understates what a signup is actually worth, because it ignores how long that person stays engaged before they unsubscribe or go inactive. This calculator takes your average monthly revenue per active subscriber and your monthly list churn rate (unsubscribes plus going permanently unengaged) to compute expected subscriber lifespan and total lifetime value, the same logic used for customer LTV but applied to the list itself. It also converts that into a maximum sustainable cost per new subscriber acquired, so you can set sane bids on lead-gen ads, giveaways, or co-registration deals without guessing. A list with 3% monthly churn has an expected lifespan of roughly 33 months, while a list bleeding 12% monthly churn only lasts about 8 months — the same monthly revenue per subscriber produces a completely different acquisition budget in each case. This matters because email is often the highest-margin channel a company has (no per-send platform tax, no auction pricing), so understating its per-subscriber value leads to under-investing in list growth relative to its real payback.
Worked example
Using the values the calculator loads with:
Inputs
- Monthly revenue per active subscriber: 1.4 $
- Monthly list churn (unsub + inactive): 3.5 %
- Contribution margin on that revenue: 55 %
- Target LTV:CAC ratio for signups: 3
Results
- Subscriber lifetime value: $22.00
- Expected subscriber lifespan: 28.6
- Max sustainable cost per new subscriber: $7.33
- Contribution value per subscriber per year: $9.24
What each field means
Inputs
- Monthly revenue per active subscriber ($)
- The monthly revenue per active subscriber used in the calculation, measured in $. Starts at 1.4 $ so you have a working example on load.
- Monthly list churn (unsub + inactive) (%)
- The monthly list churn (unsub + inactive) used in the calculation, measured in %. Starts at 3.5 % so you have a working example on load. Accepted range: 0.1–50 %.
- Contribution margin on that revenue (%)
- The contribution margin on that revenue used in the calculation, measured in %. Starts at 55 % so you have a working example on load. Accepted range: 1–100 %.
- Target LTV:CAC ratio for signups
- The target ltv:cac ratio for signups used in the calculation. Starts at 3 so you have a working example on load. Accepted range: 0.5–10.
Results
- Subscriber lifetime value
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Expected subscriber lifespan
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Max sustainable cost per new subscriber
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Contribution value per subscriber per year
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How do I measure monthly list churn accurately?
Count unsubscribes plus anyone who goes from engaged to unengaged status (no opens or clicks in 90-120 days) in a given month, divided by active subscribers at the start of the month. Don't count hard bounces from list cleaning as churn if they were never truly active.
Why include contribution margin instead of raw revenue?
Revenue per subscriber includes the cost of the product you're shipping. What you can actually afford to spend acquiring a subscriber is bounded by the profit that revenue generates, not the top-line number, same as any CAC calculation.
What's a reasonable LTV:CAC ratio for list growth tactics?
3:1 is the common floor used across acquisition channels generally. Email list growth often supports lower ratios like 2:1 to 2.5:1 because the ongoing cost to serve a subscriber (ESP fees) is near zero, unlike paid customer acquisition with real cost of goods.
Does this account for re-engagement campaigns extending lifespan?
Not directly — if you run active win-back flows that recover a meaningful share of about-to-churn subscribers, your effective churn rate should already reflect that recovery. Measure churn after re-engagement efforts, not before.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Email Subscriber Lifetime Value Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/email-subscriber-lifetime-value-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/email-subscriber-lifetime-value-calculator" target="_blank" rel="noopener">Email Subscriber Lifetime Value Calculator — RevenueLab</a> (2026).</p>
Source: [Email Subscriber Lifetime Value Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/email-subscriber-lifetime-value-calculator) (2026).