Estimates only, not financial advice. Your lender’s rate, fees and rounding will differ; ask for an official quote before you sign.
This compound interest calculator shows how savings grow from a starting amount and regular monthly deposits at a given rate, compounded daily, monthly, quarterly or yearly. It draws the balance year by year, separates deposits from interest earned and gives the APY, so you can see what time and steady contributions do.
How to use
- Loan: enter the amount, the yearly interest rate and the term in years or months. The monthly payment, total interest and payoff date appear at once.
- Add an extra monthly payment to see how much sooner you finish and how much interest you save.
- Mortgage: enter the home price and down payment (as % or amount), rate and term, then property tax, insurance, PMI and HOA to get the full monthly payment.
- Compound interest: enter a starting amount, a monthly deposit, the rate and years, and pick how often interest compounds. Move over the chart to read any year.
- Open a year in the table to see each month. Tap a row to copy it, or download the whole schedule as CSV.
- Payments use the standard fixed-rate (annuity) formula: P × r ÷ (1 − (1 + r)^−n), with r = yearly rate ÷ 12.
- PMI is added only when the down payment is under 20% and stops when the balance reaches 78% of the home price.
- Compound interest assumes deposits at the end of each month; the rate is converted to an equivalent monthly rate for the chosen compounding.
- Results don’t include origination fees, rate changes, inflation or taxes on interest.
- Rows and totals are rounded for display; the CSV keeps two decimals.
How compounding works
With compound interest, interest earns interest. The formula for a single deposit is A = P × (1 + r/n)^(n × t), where r is the yearly rate, n the compounding periods per year and t the years. 10,000 at 5% for 10 years grows to 16,288.95 compounded yearly, 16,470.09 monthly and 16,486.65 daily.
More frequent compounding raises the effective yearly rate, or APY, but only a little: 5% compounded monthly is an APY of 5.116%, daily 5.127%. Time and deposits matter far more.
Regular deposits
Adding 200 a month to the same 10,000 for 10 years at 5% monthly gives 47,526.55: 34,000 of your own money and 13,526.55 of interest. The rule of 72 gives a quick feel for growth: divide 72 by the rate to estimate how many years it takes to double, about 14.4 years at 5%. Results ignore taxes, fees and inflation.
Frequently asked questions
How do I calculate compound interest?
Use A = P × (1 + r/n)^(n × t). For 10,000 at 5% compounded monthly for 10 years: 10,000 × (1 + 0.05/12)^120 ≈ 16,470.09.
What is the difference between APR and APY?
APR is the nominal yearly rate; APY includes the effect of compounding. A 5% rate compounded daily has an APY of 5.127%.
Is daily compounding much better than monthly?
Only slightly. Over 10 years, 10,000 at 5% grows to 16,486.65 with daily and 16,470.09 with monthly compounding.
How long does it take to double my money?
Divide 72 by the yearly rate: at 6% about 12 years, at 8% about 9 years. This rule of 72 is an approximation.
When are monthly deposits added?
At the end of each month, which is the usual assumption for savings plans; the rate is converted to an equivalent monthly rate for the chosen compounding.
Does it account for taxes and inflation?
No. Interest taxes, fees and inflation reduce real returns and are not included.