We use cookies.This website uses essential cookies to operate core features. With your consent, we also use analytics cookies to understand traffic and improve the service. For more details, see our .
We use cookies.This website uses essential cookies to operate core features. With your consent, we also use analytics cookies to understand traffic and improve the service. For more details, see our .
Was this tool helpful to use?
Your feedback helps us make it better
Enter your principal, interest rate, and time period to quickly calculate simple interest and the total amount.
Select annual, monthly, or daily rate. Enter as a percentage, e.g., 3.5 for 3.5%.
Please enter the principal, interest rate, and time period to calculate simple interest.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
Simple interest applies the rate to the starting principal throughout the selected term. The calculator uses I = P × r × t, where I is interest, P is principal, r is the annual rate as a decimal, and t is time in years. The total amount is principal plus interest. Interest is not added to the balance to earn further interest.
Interest = Principal × Annual rate × Time in years
Total amount = Principal + Interest
For this calculator, a percentage rate is divided by 100; monthly rates are annualized by multiplying by 12 and daily rates by 365. Periods in months are divided by 12 and periods in days by 365. For example, $1,000 at 5% per year for 2 years gives $100 interest and a $1,100 total. Results are displayed to two decimal places.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Enter a positive starting amount. Use the same currency unit as the amount you want to interpret; the calculation itself does not select or convert currencies.
Type a percentage such as 5 for 5%, then choose annual, monthly, or daily. The rate unit tells the calculator how to express a rate before it converts it to an annual basis.
Choose days, months, or years and enter a positive duration. The tool converts days using 365 days per year and months using 12 months per year.
Review total interest, total amount, annualized rate, equivalent years, and average annual interest. Reset clears the inputs and restores annual rate and years as the selected units.
Suppose the principal is $2,000, the rate is 0.5% per month, and the term is 6 months. The calculator annualizes the rate to 6% and the term to 0.5 years. Simple interest is $2,000 × 0.06 × 0.5 = $60, making the total $2,060. The calculation retains full precision internally and formats monetary outputs to cents for display.
Use cases
See how the tool fits into real work and everyday tasks.
A learner can change one input at a time to see how principal, rate, or term affects simple interest while keeping the balance fixed.
A reader checking an illustrative agreement can estimate interest under a simple-interest assumption, then compare the result with the lender’s disclosed schedule and day-count terms.
A planner can calculate a basic interest amount for a fixed principal and period when the rate and convention are already known.
Q&A
Find concise answers to common questions and confusing cases.
No. It applies the rate to the original principal for the full term. It does not add earned interest to the balance between periods.
Contracts may use actual days, a 360-day year, leap-year rules, changing balances, payment timing, fees, or a repayment schedule. This calculator uses fixed 365-day and 12-month conversions.
No. It estimates simple interest and principal plus interest. It does not calculate installments, payoff dates, fees, APR, or amortization.
Notes
Review scope, result limitations, and important precautions before use.
Related
Discover related tools, collections, and available API capabilities.