Simple-interest guide: principal, annual rate and time

When this tool helps

Simple interest applies the rate only to the original principal. It does not earn interest on earlier interest, so it differs from compound savings even when the same annual rate is entered. This tool shows the interest separately from the final amount.

Enter the principal, annual percentage rate and time in years. A fractional year can represent part of a year: 0.5 means six months in this model. That is a year-fraction assumption, not an automatic interpretation of actual dates or a lender’s day-count convention.

What to enter

These are the candidate Android fields, not a form on this website. Editable fields in the app start empty; modes and units are selected separately.

Principal: The starting amount in one currency.
Annual interest rate (%): A non-negative yearly percentage supplied by you.
Time in years: A non-negative year count; fractional years are allowed.

Worked example · not prefilled app data

Try this example after the update is available

The values below explain the calculation. They are not a quote, a live measurement or an automatic answer for your situation.

Principal: 1000
Annual rate (%): 5
Time (years): 2

Checked example result1,100.00

At 5% per year for two years, interest on 1,000.00 is 100.00. Adding the original principal gives a final amount of 1,100.00.

Formula and assumptions

Interest = principal × annual rate ÷ 100 × years; final amount = principal + interest

No compounding, fees, taxes, variable rates, deposits or repayments are included.
The amount is a planning estimate based on your rate and time inputs, not a guaranteed return or contract quote.

A common mistake to avoid

Do not use this formula for an instalment loan and assume it gives the monthly repayment. A fixed monthly repayment model uses a different calculation.

Find this tool in the Android update

When you have the redesigned Android update, open Tools and search for Simple interest, or find it under Money.
Open the tool, choose the mode or units relevant to your task, then enter your own values.
Review the result and explanation. Use Calculate & save only if you want the calculation kept in local History; Copy result does not send it to our server.

This guide is an educational preview of the update in testing, not an announcement that Google Play has approved or published it. Calculations are in the native app; no web calculator or download is offered on this page.

Questions about Simple interest

Can I calculate six months of simple interest?

Yes. Enter 0.5 in Time in years if a half-year assumption is appropriate for your calculation.

Does earned interest also earn interest?

No. That would be compounding; this tool applies interest only to the original principal.