Examples
Examples
Try the starting example
- Acquisition spend (USD)
- 1000
- Observed net gifts by period (USD)
- 300,400,500
- Period labels
- month 1 onward
- Cumulative net gifts (USD)
- [300,700,1200]
- First payback period (index; 0 means not observed)
- 3
- Unrecovered acquisition spend (USD)
- $0.00
Try another scenario
- Acquisition spend (USD)
- 1500
- Observed net gifts by period (USD)
- 300,400,500
- Period labels
- month 1 onward
- Cumulative net gifts (USD)
- [300,700,1200]
- First payback period (index; 0 means not observed)
- 0
- Unrecovered acquisition spend (USD)
- $300.00
Calculation method
Calculation method
Cumulative net gifts (USD)
J([sum(b[:i+1]) for i in range(len(b))])
First payback period (index; 0 means not observed)
min([i+1 for i in range(len(b)) if sum(b[:i+1])>=a] or [0])
Unrecovered acquisition spend (USD)
max(0,a-sum(b))
Symbols and units
- a
- Acquisition spend (USD)
- b
- Observed net gifts by period (USD)
- c
- Period labels
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Calculation steps and notation
sum(list) adds all entries in the list.
Assumptions & limits
Assumptions & limits
- Observed cohort payback only; gifts must already be net of fulfillment costs. Negative period net gifts are allowed; reaching payback once does not ensure later retention. Supported limits: All numeric inputs must be finite. Only the explicitly described mathematical scenario is supported.
Are these inputs private?
These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.