CalcQuick · Simple interest
Simple Interest Calculator for Years, Months and Days
Use this for a constant principal that does not earn interest on interest. Enter an annual percentage and duration; for days, select the year basis that matches your scenario.
Reviewed and updated:Illustrative inputs: replace rates and costs with your own assumptions.
01
How to use this calculator
- Enter your values using the units shown.
- Review the result, which updates instantly.
- Check the formula and assumptions before using the number for a decision.
02
Formula and assumptions
Interest I = P × (annual percentage ÷ 100) × t. Total = P + I. Time t is years, months ÷ 12, or days ÷ the selected 365-day or 360-day basis.
03
Worked example
A principal of 10,000 at 5% simple annual interest for two years earns or costs 1,000 of interest. Principal plus interest is 11,000. Twelve months count as one year.
CalcQuick
Sources and scope
These references support the formula or category guidance. CalcQuick remains responsible for the calculator implementation.
- Simple interest: principal, rate and timeConsumer Financial Protection Bureau
FAQ
Frequently asked questions
How is simple interest different from compound interest?
Simple interest is calculated only on the original principal. Compound interest also earns or charges interest on accumulated interest; use the interest calculator for that scenario.
Should I choose a 360-day or 365-day year?
Use the basis specified by the agreement or scenario you are modeling. The calculator does not infer a banking or legal convention from your language or currency.
Does the total represent monthly loan repayments?
No. It is unchanged principal plus simple interest. A loan with a declining balance needs a repayment schedule, which is available in the loan calculator.