🌱Compound Interest Calculator

Project the future value of a deposit with compound interest: choose annual, semi-annual, quarterly, monthly, weekly or daily compounding and see total interest earned.

Worked examples

10,000 at 5% for 10 years, monthly

GET /api/v1/calculators/compound-interest-calculator?principal=10000&annualRate=5&years=10&timesPerYear=12

Result: 16,470.09

5,000 at 7% for 20 years, annually

GET /api/v1/calculators/compound-interest-calculator?principal=5000&annualRate=7&years=20&timesPerYear=1

Result: 19,348.42

50,000 at 3% for 5 years, daily

GET /api/v1/calculators/compound-interest-calculator?principal=50000&annualRate=3&years=5&timesPerYear=365

Result: 58,091.35

Machine API (x402)

$0.002 / call

This tool is also a JSON API for AI agents. Requests without payment receive 402 Payment Required plus instructions; agents pay USDC on Base via the x402 protocol — no accounts, no API keys.

GET /api/v1/calculators/compound-interest-calculator?principal=10000&annualRate=5&years=10&timesPerYear=12 HTTP/1.1
Host: agenttools-hub.vercel.app

→ 402 (payment required, instructions in headers)
→ 200 (after X-PAYMENT header; JSON body below)

{
  "tool": "calculators/compound-interest-calculator",
  "input": {"principal":10000,"annualRate":5,"years":10,"timesPerYear":12},
  "result": { "value": 16470.094977, "answer": "16,470.09" }
}

Agent docs: /llms.txt · OpenAPI spec · integration guide

About this tool

Compound interest reinvests earned interest every period, so growth accelerates over time. This calculator supports the six standard compounding frequencies and compares the result against simple interest so you can see the compounding effect.

A = P × (1 + r/n)^(n·t), where r = annual rate, n = compounds per year, t = years

Frequently asked questions

Which compounding frequency earns the most?

More frequent compounding always earns more at the same nominal rate, but the gain shrinks: monthly vs daily is nearly identical for typical rates.

What is the difference from APY?

APY is the effective annual yield including compounding. A 5% nominal rate compounded monthly equals ≈5.116% APY.

Does this include regular deposits?

No — this is a single-deposit projection. Regular contributions use a future-value-of-annuity formula (planned for a separate tool).

Related tools

📈 CAGR Calculator 💠 ROI Calculator