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Primary formula: payback = first interpolated period where cumulative retained contribution crosses CAC
Duc Nguyen X.By Duc Nguyen X.· Founder, Margin101Last reviewed: View update historyMethodology

Educational only: Business decision support, not accounting, tax or legal advice.

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Update policy: Reviewed when formulas or official dependencies change.

Scope: Market-neutral small-business planning using your own assumptions.

What this planner helps you decide

Best for

Teams testing when retained contribution recovers CAC.

Outputs

Period contribution sequence, interpolated payback and unrecovered CAC.

Start here

Set a finite horizon, ramp and collection delay.

Use a different tool when: Do not use this to include customer onboarding cost in a SaaS payback period; use Customer Onboarding Payback Planner for that decision. Use this tool to find when retained customer contribution recovers acquisition cost.

Cash & growth

CAC Payback: period contribution sequence

Period contribution sequence, interpolated payback and unrecovered CAC.

Amounts use the same currency as your inputs. No currency conversion is performed.

Decision assumptions

Use one consistent period, contribution and currency basis.

Your numbers stay in this browser

currency units

Cost to recover. Use one consistent currency and indirect-tax basis.

currency units

Contribution before retention weighting. Use one consistent currency and indirect-tax basis.

%

Retained share carried forward.

Finite whole-number horizon.

Whole periods until full contribution.

Whole periods before contribution starts.

Decision result

Every result is produced by the registered customer and marketing engine.

Preparing export actions…
CAC payback
2.94 periods
Cumulative Contribution
184.46
Unrecovered CAC
0.00
Unrecovered CAC Share
0%
Target CAC
120.00
Cumulative contribution against CAC

The line shows when cumulative customer contribution reaches the acquisition-cost target.

Cumulative contribution
CAC target
120.00
Data for Cumulative contribution against CAC
PeriodCumulative contribution
150.00
290.00
3122.00
4147.60
5168.08
6184.46
Cumulative contribution by period
PeriodContributionCumulative Contribution
150.0050.00
240.0090.00
332.00122.00
425.60147.60
520.48168.08
616.38184.46

Scenario comparison

Each row names the assumption axis changed from the baseline.

ScenarioResultDifference
Entered scenario2.94 periodsBaseline
Lower Customer acquisition cost2.56 periodsNot available
Higher Customer acquisition cost3.39 periodsNot available

Save these results, change an input, then compare the updated figures with this baseline.

The baseline is temporary in this tab and is not added to shared scenario links or generated reports.

Calculation details

View calculation detailsView the formulas and inputs used for these results.

CAC payback

Payback Periodsinterpolated cumulative contribution crossing2.94 periods
Result2.94 periods

Reports periods for the declared cohort and period using the entered attribution and contribution basis. The engine retains raw precision; formatting never feeds calculation.

CAC Payback Planner formulas →
Inputs used by these formula steps
Payback PeriodsCustomer Acquisition Cost
120
Payback PeriodsContribution Per Customer Period
50
Payback PeriodsRetention Rate
0.8
Payback PeriodsHorizon Periods
6
Payback PeriodsRamp Periods
0
Payback PeriodsPayment Delay Periods
0

Cumulative Contribution

Cumulative Contributionsum of period contributions184.46
Result184.46

Reports money for the declared cohort and period using the entered attribution and contribution basis. The engine retains raw precision; formatting never feeds calculation.

CAC Payback Planner formulas →
Inputs used by these formula steps
Cumulative ContributionCustomer Acquisition Cost
120
Cumulative ContributionContribution Per Customer Period
50
Cumulative ContributionRetention Rate
0.8
Cumulative ContributionHorizon Periods
6
Cumulative ContributionRamp Periods
0
Cumulative ContributionPayment Delay Periods
0

Unrecovered CAC

Unrecovered CACmax(0, CAC − cumulative contribution)0.00
Result0.00

Reports money for the declared cohort and period using the entered attribution and contribution basis. The engine retains raw precision; formatting never feeds calculation.

CAC Payback Planner formulas →
Inputs used by these formula steps
Unrecovered CACCustomer Acquisition Cost
120
Unrecovered CACContribution Per Customer Period
50
Unrecovered CACRetention Rate
0.8
Unrecovered CACHorizon Periods
6
Unrecovered CACRamp Periods
0
Unrecovered CACPayment Delay Periods
0

Unrecovered CAC Share

Unrecovered CAC Shareunrecovered CAC ÷ CAC0 percent
Result0%

Reports percent for the declared cohort and period using the entered attribution and contribution basis. The engine retains raw precision; formatting never feeds calculation.

CAC Payback Planner formulas →
Inputs used by these formula steps
Unrecovered CAC ShareCustomer Acquisition Cost
120
Unrecovered CAC ShareContribution Per Customer Period
50
Unrecovered CAC ShareRetention Rate
0.8
Unrecovered CAC ShareHorizon Periods
6
Unrecovered CAC ShareRamp Periods
0
Unrecovered CAC SharePayment Delay Periods
0

Target CAC

Target CACentered CAC120.00
Result120.00

Reports money for the declared cohort and period using the entered attribution and contribution basis. The engine retains raw precision; formatting never feeds calculation.

CAC Payback Planner formulas →
Inputs used by these formula steps
Target CACCustomer Acquisition Cost
120
Target CACContribution Per Customer Period
50
Target CACRetention Rate
0.8
Target CACHorizon Periods
6
Target CACRamp Periods
0
Target CACPayment Delay Periods
0

Inputs used

Customer Acquisition Cost
120
Contribution Per Customer Period
50
Retention Rate
0.8
Horizon Periods
6
Ramp Periods
0
Payment Delay Periods
0

SaaS CAC payback cohort

Compare acquisition and onboarding cost with retained gross contribution. All cohort assumptions are editable and no benchmark is embedded.

This embedded cohort stays local to the page and is not included in the owner scenario URL, saved comparison or PDF report.

currency units
currency units
currency units
%
%
months

CAC payback: 3.8 months

Calculation details

View calculation detailsView the formulas and inputs used for these results.

SaaS CAC payback month

SaaS CAC payback monthpayback month = first fractional month where cumulative retained gross contribution recovers acquisition + onboarding cost; otherwise null3.76
Result3.8 months

Calculated only from editable, user-entered owner-module values. Display rounding does not feed back into the engine.

Owner methodology →
Inputs used by these formula steps
SaaS CAC payback monthAcquisition Cost
600
SaaS CAC payback monthOnboarding Cost
100
SaaS CAC payback monthMrr
250
SaaS CAC payback monthGross Margin Percent
80
SaaS CAC payback monthRetention Percent
95
SaaS CAC payback monthHorizon Months
24

Inputs used

acquisitionCost
600
onboardingCost
100
mrr
250
grossMarginPercent
80
retentionPercent
95
horizonMonths
24
Open this calculator with preset values

This calculator supports documented, shareable scenario URLs. Compatible assistants and applications can construct links using the parameters below.

Scenario links contain only allowlisted numeric and closed-choice inputs shown in the URL; Margin101 excludes free text and identifying fields. Anyone you share the URL with can read those numbers, so do not include private or identifying data.

Example: https://margin101.com/tools/cac-payback/?sv=1&contributionPerCustomerPeriod=50&customerAcquisitionCost=120&horizonPeriods=6&paymentDelayPeriods=0&rampPeriods=0&retentionRate=0.8

ParameterMeaningUnitAllowed valuesPresenceDefault
contributionPerCustomerPeriodContribution before retention weighting. Use one consistent currency and indirect-tax basis.currency units/customer/period0 to 10000000Required50
customerAcquisitionCostCost to recover. Use one consistent currency and indirect-tax basis.currency units/acquired customer0 to 10000000Required120
horizonPeriodsFinite whole-number horizon.periods0 to 120Required6
paymentDelayPeriodsWhole periods before contribution starts.periods0 to 120Required0
rampPeriodsWhole periods until full contribution.periods0 to 120Required0
retentionRateRetained share carried forward.decimal share retained/period0 to 1Required0.8

CAC Payback: period contribution sequence

CAC payback identifies the interpolated period where the finite retained-contribution sequence recovers acquisition cost.

Formula summary

Primary formula
payback = first interpolated period where cumulative retained contribution crosses CAC

Read the full methodology

Data used here

  • The estimate uses your inputs and the general business formula documented in the methodology.

Decision checks

Act on the result

Use CAC payback and unrecovered CAC to cap acquisition cost or require a longer contract and collection horizon.

Stress-test the decision

Retest contribution per customer per period in currency units and retention rate per period as a percentage.

When this estimate can be misleading

  • Attribution, incrementality, conversion and retention are user-entered assumptions, not causal claims or forecasts.
  • Use one consistent period, currency, contribution and indirect-tax basis.
  • This is educational decision support, not financial, tax, legal or accounting advice.
  • CAC payback identifies the interpolated period where the finite retained-contribution sequence recovers acquisition cost.

Educational estimate, not advice. See all assumptions & limitations →

Related reading

Guides to interpret the decision and its assumptions.

Frequently asked questions

How do I find when retained customer contribution recovers acquisition cost?

Use CAC payback and unrecovered CAC to cap acquisition cost or require a longer contract and collection horizon.

Which planning assumptions should I stress-test?

Compare a plausible alternative scenario and verify the decision-critical assumption that changes the plan most.