calc.engineer / General & Math / Compound Interest

Compound Interest v1.0.0

Calculates compound interest growth over time using the formula A = P(1 + r/n)^(nt). Given a principal, annual rate, duration in years, and compounding frequency, returns the future value, total interest earned, effective annual rate (APY), and a year-by-year growth schedule. Supports optional recurring monthly contributions for savings projections. Works for savings accounts, CDs, investment returns, and retirement planning. Currency-agnostic.

Initial investment or deposit amount (any currency unit).
Annual interest rate as a percentage (e.g., 5.5 for 5.5%).
Investment duration in years. Max 100.
How often interest compounds per year. Allowed: 1 (annually), 2 (semi-annually), 4 (quarterly), 12 (monthly), 52 (weekly), 365 (daily). Defaults to 12.
Optional recurring monthly contribution added at each month. Defaults to 0.
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/compound_interest \
  -H "Content-Type: application/json" \
  -d '{"principal": …, "annual_rate_pct": …, "years": …}'

MCP: connect to https://calc.engineer/mcp and call compound_interest.

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