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Tech Debt Interest

Estimate how much extra repair time a shortcut can create later.

Payoff hours = initial fix × (1 + effective growth)^months. Effective growth compounds with code velocity — more features landing on the hack accelerate the drag.

Part of: Saving & Spending Calculators

Start below
Fields marked optional can be skipped; results update as you type
TECH_DEBT_INTEREST
Quantifies the compounding cost of shipping a hack now
DEBT PAYOFF AT MONTH 18
46.1 hrs7.7× the original 6hr fix
Debt date: Jan 2028. Effective compounding rate 12.0%/mo (includes velocity multiplier).
Payoff exceeds 4× original fix. Schedule repayment before more features build on top.
MAINTENANCE BURDEN HEATMAP
M16h
M27h
M38h
M48h
M59h
M611h
M712h
M813h
M915h
M1017h
M1119h
M1221h
M1323h
M1426h
M1529h
M1633h
M1737h
M1841h
<10h10–25h25–60h60h+
▸ METHODOLOGY
Payoff hours = initial fix × (1 + effective growth)^months. Effective growth = base monthly growth × (1 + velocity/10) — each new feature built on top compounds the tangle. Interest accelerates when multiple features hit the same hack; isolated shortcuts decay slower.

Before you trust the result

Check the inputs that matter most: dates, rates, units, costs, and any optional fields you skipped. A calculator can only work with the numbers entered here, so use the result as a decision check rather than a final answer when money, health, tax, legal, or safety consequences are involved.

If the result feels surprising, change one input at a time and watch which number moves. That usually shows the real lever behind the decision.

More about this tool

How to use this tool
  1. Enter Initial Fix Hours and Monthly Growth %.
  2. Set Code Velocity — new features built on top per month.
  3. Set how many months you plan to wait before paying it down.
  4. The heatmap shades each month by maintenance burden band.

Examples

6hr fix, 8%/mo growth, 18 months wait, velocity 5
Payoff ≈ 22hrs — almost 4× the original, with a red-band heatmap past month 12.

Next up

Debt too steep? Decide hire, automate, or rebuild.Hire vs Automate → Interest compounding? Check if output per head is falling.Revenue per Head →

Frequently asked questions

› What is a good growth rate? Definition

5–10%/mo for actively-developed modules; near 0 for stable utilities. High-churn areas compound fastest.

› Is this an exact estimate? Trust & accuracy

No — it is an order-of-magnitude tool to force the conversation about scheduling repayment.

Tips & related reading

See the Saving & Spending Calculators hub →

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