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Build Versus Subscription Payback

Compare estimated internal build cost and annual maintenance with an external annual subscription.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.

Formula and method

The displayed ten-week build costs 1,120. Annual maintenance is 268.80, leaving annual subscription savings of 1,120 and a one-year simple payback.

Build cost = weeks × weekly loaded staff cost × staff count; annual maintenance = days per month × weekly cost × 12/5; payback = build cost / annual savings.

Worked example

Enter these known values and leave the other values blank.

Cost
1388.8 USD / yrs
Employees required
1
Time to build
10 wks
Employee salary (gross)
487 USD / mos
Overhead
0 %
Days of maintentance
1 / mos
Effective cost per employee
487 USD / mos
Cost to build
1120 USD
Annual maintenance
268.8 USD / yrs
Annual savings
1120 USD
Years to profit
1 yrs

Assumptions and limitations

  • The salary period selector converts the entered pay to a weekly cost; the default salary period is monthly. Enter maintenance as days per month; the estimate assumes five working days per week and twelve months per year.
  • Payback ignores discounting, uncertainty, licensing, future staff changes and nonfinancial advantages. A nonpositive annual saving cannot repay the build cost.
  • Use one currency throughout. Retained currency selector factors are a historical snapshot, not live exchange rates.
  • Clear an editable unknown before solving an inverse. Selection controls and forced outputs cannot be inferred.

Common questions

What does this model assume?

The salary period selector converts the entered pay to a weekly cost; the default salary period is monthly. Enter maintenance as days per month; the estimate assumes five working days per week and twelve months per year.

Can I use the currency menu as a current quote?

No. Keep amounts in one currency; conversion factors are a captured historical snapshot.

References

The calculation follows this reviewed mathematical model: Build cost = weeks × weekly loaded staff cost × staff count; annual maintenance = days per month × weekly cost × 12/5; payback = build cost / annual savings. Required model inputs: Staff count must be a positive whole number. Positive annual savings are required for finite payback.

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