# Simple Interest Calculator

> Calculate simple interest and see how it differs from compound interest.

To calculate simple interest, enter the principal, annual rate and time in years. Simple interest applies only to the original principal, so it grows linearly — the tool also shows what compound interest would have produced, which is almost always more.

**URL:** https://convertto.tech/t/simple-interest-calculator
**Category:** Calculators (https://convertto.tech/c/calculators)
**Privacy:** Runs entirely in the browser; no upload
**Cost:** Free, no sign-up
**Last updated:** 2026-08-01

## Key facts

- **Privacy:** Runs entirely in your browser — nothing is uploaded
- **Cost:** Free, unlimited, no sign-up

## How to use

1. Set the principal.
2. Set the annual rate.
3. Set the time.
4. The result appears immediately — copy or download it.

## FAQ

### How does simple interest differ from compound?

Simple interest is calculated only on the original principal, so it grows linearly. Compound interest is calculated on principal plus accumulated interest, so it grows exponentially. Over one year they are close; over thirty they are not remotely comparable.

### Where is simple interest actually used?

Short-term instruments — many car loans, some bonds, and most late-payment penalties. Anything spanning years is almost always compound, which is why quoting a simple rate on a long loan understates its cost.

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