Compound Interest Calculator
Project future value from a deposit and regular contributions at a hypothetical rate, with annual to daily compounding, start or end timing, APY and a yearly table.
Interactive calculator · Method COMPOUND-INTEREST-1.0 · Last reviewed: 2026-11-04
Calculate your scenario
With annual rate R, compounding m times a year and contributions p times a year, the rate per contribution period is i = (1 + R ÷ m)^(m ÷ p) − 1.
Your inputs
Default worked example. Edit the inputs to calculate your scenario.
Default worked example
$10,000.00 × 1.00416667^120 + $200.00 × ((1 + 0.00416667)^120 − 1) ÷ 0.00416667 = $47,526.55.
How to use the calculator
Enter the initial deposit and any recurring contribution, choose how often and when contributions are made, then enter a rate to test, the compounding frequency and the number of years.
What the result means
Starting with $10,000 and adding $200 at the end of each month at a hypothetical 5% compounded monthly gives about $47,526.55 after 10 years: $34,000 put in and $13,526.55 of interest.
Formula and units
With annual rate R, compounding m times a year and contributions p times a year, the rate per contribution period is i = (1 + R ÷ m)^(m ÷ p) − 1. Future value = initial × (1 + R ÷ m)^(m × years) + contribution × ((1 + i)^(p × years) − 1) ÷ i, multiplied by (1 + i) when contributions are made at the start of each period. APY = (1 + R ÷ m)^m − 1. Interest earned = future value − all money put in.
Worked examples
$10,000 plus $200 a month at 5% for 10 years: Initial deposit: 10000 $; Recurring contribution: 200 $; Annual interest rate (hypothetical example): 5 %; Years: 10 years; Contribution frequency: monthly; Contribution timing: end; Compounding: 12.
Example result: Future value: $47,526.55; Total contributions (incl. initial deposit): $34,000.00; Interest earned: $13,526.55; Effective annual yield (APY): 5.1162%; Rate per contribution period: 0.416667%.
$5,000 at the start of each year at 6% quarterly for 20 years: Initial deposit: 0 $; Recurring contribution: 5000 $; Annual interest rate (hypothetical example): 6 %; Years: 20 years; Contribution frequency: annual; Contribution timing: start; Compounding: 4.
Example result: Future value: $198,100.17; Total contributions (incl. initial deposit): $100,000.00; Interest earned: $98,100.17; Effective annual yield (APY): 6.1364%; Rate per contribution period: 6.136355%.
Limitations and common mistakes
The rate is a hypothetical constant you enter, not a promised or typical return. Taxes, fees, inflation, early-withdrawal penalties and rate changes are not modeled. Contributions between compounding dates are credited through the equivalent rate per contribution period, which matches compounding exactly at period ends; a bank’s day-count rules can differ slightly.
Comparing a nominal rate with one account’s APY: 5% compounded monthly is a 5.1162% APY, so compare APY to APY.
Sources and assumptions
Method COMPOUND-INTEREST-1.0; last formula review 2026-11-04. Sources and their supported claims. Calculation methodology.