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
CAC payback period
2.6
Lifetime value
$170
Expected customer lifetime
10.0
Contribution margin per box
$17.00
LTV : CAC ratio
3.78
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How to use this
- 1Enter monthly subscription price ($).
- 2Enter cost per box (product+pack+ship) ($).
- 3Enter customer acquisition cost ($).
- 4Enter monthly churn rate (%).
- 5Read your cac payback period on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Subscription boxes live and die on payback period and churn, not just gross margin on the box itself. A box that's profitable on paper can still bankrupt a company if it takes eight months to recover acquisition cost and average customers churn at month five. This calculator takes your monthly subscription price, cost per box (product + packaging + shipping), customer acquisition cost, and monthly churn rate, and computes contribution margin per box, expected customer lifetime in months, total lifetime value, and CAC payback period in months. Enter subscription price, cost per box, CAC, and monthly churn rate as a percentage. The output shows months to recover CAC and total LTV, which together tell you whether your growth is sustainable or whether you're funding growth by burning cash faster than subscriptions replace it, a common failure mode in box subscription businesses that scale acquisition before fixing retention.
Worked example
Using the values the calculator loads with:
Inputs
- Monthly subscription price: 39 $
- Cost per box (product+pack+ship): 22 $
- Customer acquisition cost: 45 $
- Monthly churn rate: 10 %
Results
- CAC payback period: 2.6
- Lifetime value: $170
- Expected customer lifetime: 10
- Contribution margin per box: $17.00
- LTV : CAC ratio: 3.78
What each field means
Inputs
- Monthly subscription price ($)
- The monthly subscription price used in the calculation, measured in $. Starts at 39 $ so you have a working example on load.
- Cost per box (product+pack+ship) ($)
- The cost per box (product+pack+ship) used in the calculation, measured in $. Starts at 22 $ so you have a working example on load.
- Customer acquisition cost ($)
- The customer acquisition cost used in the calculation, measured in $. Starts at 45 $ so you have a working example on load.
- Monthly churn rate (%)
- The monthly churn rate used in the calculation, measured in %. Starts at 10 % so you have a working example on load. Accepted range: 0.5–100 %.
Results
- CAC payback period
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Lifetime value
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Expected customer lifetime
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Contribution margin per box
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- LTV : CAC ratio
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What's a safe CAC payback period for a subscription box?
Under 3 months is strong, 3-6 months is workable if you have cash reserves to fund the gap, and over 6 months is risky unless you have outside funding, since you're financing growth from your balance sheet rather than from the subscriptions themselves.
How does churn rate affect LTV so dramatically?
Expected lifetime is the inverse of churn rate, so dropping monthly churn from 10% to 7% extends expected lifetime from 10 months to over 14 months, a 40%+ LTV increase from a change that often costs less to achieve than acquiring more customers.
Is 1 ÷ churn rate an accurate lifetime estimate?
It's a standard approximation assuming constant (geometric) churn each month, which is reasonably accurate for many subscription businesses after the first couple of months, though early cancellation spikes in month one or two can make real average lifetime a bit shorter than this formula suggests.
What's a good LTV:CAC ratio for a box subscription?
3:1 or higher is the standard healthy benchmark. Below 2:1 usually means you need to either raise price, cut churn, or lower acquisition cost before scaling ad spend further, since growth just accelerates the cash burn.
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.
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Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Subscription Box Unit Economics Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/subscription-box-unit-economics
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/subscription-box-unit-economics" target="_blank" rel="noopener">Subscription Box Unit Economics Calculator — RevenueLab</a> (2026).</p>
Source: [Subscription Box Unit Economics Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/subscription-box-unit-economics) (2026).