Find the interest rate calculator in the app. Available with Premium in The Percentage Calculator app.
A monthly plan or lifetime Premium purchase is required for this feature.
The interest rate calculator requires Premium. Before entering numbers, check the app’s field labels for the interest model and time units.
Open this function in the app and read the labels for the calculation you need.
Check whether the rate is yearly or monthly. The example below uses simple annual interest.
Use APR or APY only when that measure is explicitly identified. A stated interest rate alone does not establish either measure.
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Interest calculations depend on the amount, the period and the interest model. An annual rate and a monthly rate are not interchangeable, and simple and compound interest use different methods.
The example below uses simple interest. Follow the app’s field labels for its calculation type; APR, APY and fees require their own conventions.
An interest calculator needs a stated time period and model. The rate relates interest to the principal over that period. A rate without its time period is incomplete: 5% per year and 5% per month describe different costs or growth.
Principal is the starting amount. Interest is the additional amount charged or earned under the stated calculation. To interpret a rate, check whether the calculation uses a fixed principal, a changing balance or interest added back to the balance.
The mobile app includes an interest rate tool with Premium. Follow the labels and instructions inside that tool. The mathematical examples below show why the interest model matters.
For simple interest, 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. Rearranging gives r = I ÷ (P × t).
If a fixed principal of 1,000 earns 100 over two years under a simple interest agreement, r = 100 ÷ (1,000 × 2) = 0.05, or 5% per year. This assumes no compounding, contributions, withdrawals or fees.
A one-year increase from 1,000 to 1,050 is also 5% growth. Over several years, total growth and annual rate differ. Under annual compounding, a balance growing from 1,000 to 1,102.50 over two years corresponds to 5% per year in that model.
Banks may quote different types of rates for borrowing and savings accounts. In US lending, APR incorporates the interest rate and certain additional loan charges. APY expresses an annual yield that reflects compounding. Compare rates stated on the same basis and read the product terms.
The CFPB’s interest rate and APR explanation describes why a mortgage’s APR can differ from its interest rate. Its annual percentage yield definition explains the role of compounding. Check which costs and compounding assumptions are included in any rate you compare.
Use the compound interest explanation for interest added to the balance. For a standard repayment example, see the mortgage page. To compare two known amounts without interpreting the result as an interest rate, use the free percentage change calculator.
Not necessarily. Those measures use specific conventions and may account for fees or compounding. Check exactly which measure an app or lender is reporting.
Open the app and unlock Premium, then follow the interest rate tool’s field labels. This page explains the mathematics with fixed examples. Four other percentage calculators are free online and in the app.
Under a simple annual interest model, 10,000 × 0.04 × 1 gives 400 of interest over one year. The ending balance is 10,400 before any fees or taxes, assuming no deposits or withdrawals.
That division gives a periodic rate under a nominal annual-rate convention with monthly periods. An effective annual rate needs a different conversion: monthly rate = (1 + annual decimal rate)^(1/12) − 1. Check which convention applies.
No. With no cash flows, the annual compound growth rate is the square root of 1.10 minus 1, or about 4.88%. A 5% annual compound rate produces 10.25% total growth over two years.
