How to use the calculator
Choose a mode, enter the required values, and click Calculate. The Result section appears after a successful calculation.
Choose a calculation mode
- Select Simple Interest for growth on the original principal. Enter the required fields other than the value selected in Solve for.
- Select Compound Interest for growth after each compounding period. Enter the same values and choose a Compounding frequency.
- Select APY (Effective Yield) to calculate an effective annual yield. Enter Nominal annual rate (%) and Compounding frequency. Principal ($) and Term are optional; enter both to show a dollar future value and growth schedule.
- Select APR (Borrowing Cost) for the fixed-payment borrowing model. Enter Principal / loan amount ($), Nominal annual rate (%), Term, and Payment frequency. Add Upfront fees ($, optional) if needed.
Solve for a missing value
In Simple Interest and Compound Interest, use Solve for to choose Future value, Principal, Rate, or Time. The selected field is cleared and disabled. Enter the remaining required fields, then click Calculate.
- Future value: enter Principal ($), Nominal annual rate (%), and Term.
- Principal: enter Future value ($), Nominal annual rate (%), and Term.
- Rate: enter Principal ($), Future value ($), and Term.
- Time: enter Principal ($), Future value ($), and Nominal annual rate (%).
For Rate and Time, Future value ($) must be greater than Principal ($). Time also requires a rate greater than 0.
Read the result and schedule
- Simple Interest: shows future value, principal, nominal annual rate, effective annual rate equal to the nominal rate, total interest, and a yearly growth schedule.
- Compound Interest: shows future value, principal, nominal annual rate, effective annual rate, total interest, and a schedule per compounding period.
- APY (Effective Yield): shows effective annual yield, nominal annual rate, and the effective-versus-nominal gap. Principal and Term add a future value and growth schedule when both are supplied.
- APR (Borrowing Cost): shows effective APR, nominal rate, payment per period, total finance charge, assumptions, and a payment schedule. Fees reduce the net amount financed, while the payment uses the full principal.
Validation errors hide the Result section until a successful calculation.
Understand rates, terms, and schedule periods
- Simple Interest uses
A = P x (1 + r x t). Compound Interest usesA = P x (1 + r/n)^(n x t). APY usesAPY = (1 + r/n)^n - 1. - Terms entered in months are converted to fractional years for formulas. Simple Interest schedules use yearly rows based on a rounded year count. Compound Interest and APY schedules use compounding-period rows based on a rounded period count.
- APR rounds the term to a whole payment-period count before calculating the schedule. It solves the periodic APR numerically from the fixed payments.
- Compounding frequencies are annually (1/year), semi-annually (2/year), quarterly (4/year), monthly (12/year), bi-weekly (26/year), weekly (52/year), and daily (365/year).
- Payment frequencies are monthly (12/year), bi-weekly (26/year), weekly (52/year), quarterly (4/year), and annually (1/year).
Validation, limits, and Reset
When required, Principal and Future value must be greater than 0. Nominal annual rate (%) must be from 0 to 100 percent, Term must be greater than 0, and Upfront fees ($, optional) must be nonnegative and less than the principal.
Growth schedules display at most 600 rows. APR rejects more than 4,800 payment periods. The calculator assumes a fixed rate and evenly spaced periods; it does not model variable rates, irregular contributions, taxes, or account-specific terms.
Click Reset to clear numeric inputs and fees, restore Solve for to Future value, restore Term unit to Years, restore both frequencies to Monthly (12/year), hide the result, and clear errors. Reset keeps the currently selected mode.
Copy or download the result
After calculating, use Copy result to copy the plain-text summary with the browser clipboard. If clipboard access fails, the tool can show a manual-copy fallback. Use Download result (.txt) to download the summary. Exported text excludes schedule rows, APY Principal and Term, and APR total payments.
Data handling and scope
Calculations run in the browser from the values you enter. The tool does not fetch live rates, estimate lender fees, compare loan or savings offers, or provide personalized lending or investment advice. The page also loads Ahrefs and Google Analytics scripts, and its newsletter form submits an email to /assets/subscribe.php.
Frequently Asked Questions
What is the difference between simple and compound interest?
Simple interest is earned only on the original principal, so it grows linearly: A = P(1 + rt). Compound interest is earned on the principal plus previously earned interest, so it grows exponentially: A = P(1 + r/n)^(nt), where n is the number of times interest compounds per year.
What is the difference between the nominal rate and APY?
The nominal rate is the stated annual rate before accounting for compounding within the year. APY (annual percentage yield) is the effective rate you actually earn once compounding is applied: APY = (1 + r/n)^n - 1. The more often interest compounds, the further APY rises above the nominal rate.
How does this calculator compute APR when there are fees?
The calculator sizes the periodic payment from the nominal rate, treats fees as reducing the amount received, and solves numerically for the periodic rate at which the scheduled payments discount back to that reduced amount. That rate is annualized as APR and represents the borrowing cost in this mathematical model.
Can I solve for the rate or time instead of the final value?
Yes. In the Simple Interest and Compound Interest modes, use Solve for to choose whether the calculator finds the future value, the required principal, the rate needed, or the time needed, given the other values you provide.
Does this tool give lending or investment advice?
No. It performs a transparent mathematical calculation on the numbers you enter. It does not fetch live rates, estimate lender fees, compare loan or savings offers, or provide personalized financial, investment, or lending advice.