Compound Interest Calculator
See how a deposit and regular contributions grow with compound interest at any compounding frequency, with a yearly table and chart, or convert an interest rate between compounding frequencies.
Change the values and press Calculate to work out your own figures.
Grow savings
Enter a starting amount, the interest rate and how often interest is added. Optionally add a regular contribution to see how your savings grow year by year.
- Balance
- Total deposited
- Total interest
Over 10 years the balance grows to $31,998.32: $22,000.00 deposited and $9,998.32 of interest.
| Year | Added | Interest | Balance | Total deposited | Total interest |
|---|---|---|---|---|---|
| 1 | $1,200.00 | $539.50 | $11,739.50 | $11,200.00 | $539.50 |
| 2 | $1,200.00 | $628.51 | $13,568.01 | $12,400.00 | $1,168.01 |
| 3 | $1,200.00 | $722.05 | $15,490.06 | $13,600.00 | $1,890.06 |
| 4 | $1,200.00 | $820.38 | $17,510.44 | $14,800.00 | $2,710.44 |
| 5 | $1,200.00 | $923.76 | $19,634.20 | $16,000.00 | $3,634.20 |
| 6 | $1,200.00 | $1,032.40 | $21,866.60 | $17,200.00 | $4,666.60 |
| 7 | $1,200.00 | $1,146.63 | $24,213.23 | $18,400.00 | $5,813.23 |
| 8 | $1,200.00 | $1,266.68 | $26,679.91 | $19,600.00 | $7,079.91 |
| 9 | $1,200.00 | $1,392.88 | $29,272.79 | $20,800.00 | $8,472.79 |
| 10 | $1,200.00 | $1,525.53 | $31,998.32 | $22,000.00 | $9,998.32 |
Show the working
- Effective annual rate = (1 + 0.05/12)^12 − 1 = 5.116190% (12 compounding periods a year)
- Growth per contribution period (12 a year): g = (1 + r/12)^(12/12) = 1.00416666667
- Deposit: $10,000.00 × g^120 = $16,470.09
- Contributions: $100.00 × (g^120 − 1) ÷ (g − 1) = $15,528.23
- Rounded to the cent: $31,998.32; interest = $31,998.32 − $22,000.00 deposited = $9,998.32
Convert a rate between compounding frequencies
Turn a rate compounded one way into the equivalent rate compounded another way, for example a monthly rate into its APY.
Show the working
- Effective annual rate of 6% compounded monthly: (1 + r/12)^12 − 1 = 6.1677811864%
- Equivalent rate compounded annually (APY): 1 × ((1 + EAR)^(1/1) − 1) = 6.1677811864%
How compound interest works
With compound interest, the interest you earn is added to your balance, and from then on it earns interest too. The more often interest is added (compounded), the faster the balance grows, although the difference between monthly and daily compounding is small.
- Enter your starting amount, the annual interest rate and how often interest is compounded.
- Enter the number of whole years.
- To include regular savings, add a contribution amount, how often you add it, and whether it goes in at the start or the end of each period.
- Read the ending balance, how much of it you deposited and how much is interest, then check the year-by-year table and chart.
Compound interest formulas
Balance of a single deposit: P × (1 + r/m)^(m × t) Continuous compounding: P × e^(r × t) Effective annual rate (APY): (1 + r/m)^m − 1 Regular contributions C, n of them: C × ((1 + i)^n − 1) ÷ i, where i is the growth per contribution period P = starting amount, r = annual rate, m = compounding periods per year, t = years
For example, $10,000 at 5% compounded monthly, plus $100 at the end of every month, grows to $31,998.32 after 10 years. You deposit $22,000 in total, so $9,998.32 is interest. Making the same deposits at the start of each month gives $32,063.02, because each deposit earns one more month of interest.
Converting between compounding frequencies
Rates compounded in different ways can't be compared directly. The second calculator converts a rate to the equivalent rate at another frequency. Converting to annual compounding gives the APY (annual percentage yield), the figure banks use to compare savings accounts: 6% compounded monthly is the same as 6.16778% compounded once a year.
Assumptions
The rate and contributions stay the same for the whole period, and taxes, fees, withdrawals and inflation are not included. Daily compounding uses 365 days in every year. When you add money more often than interest is compounded, the calculator lets it earn interest from the day it is added, at the equivalent rate; an account that pays nothing until the next compounding date would pay slightly less.
Questions
What is the difference between APR and APY?
APR here is the nominal annual rate before compounding. APY is what you actually earn in a year once compounding is included, so it is higher whenever interest is compounded more than once a year.
How long does it take to double my money?
A quick estimate is the rule of 72: divide 72 by the annual rate. At 6% that is about 12 years. Enter your numbers above to see the exact balance for each year.
Does compounding more often make a big difference?
Less than most people expect. $1,000 at 6% for 2 years grows to $1,123.60 compounded annually, $1,127.49 compounded daily and $1,127.50 compounded continuously.
Sources
Limitations
- Constant rate and constant contributions for the whole horizon; no contribution growth, withdrawals, taxes, fees or inflation adjustment.
- Whole years only (1–100); partial-year horizons are not modelled.
- When contributions are more frequent than compounding, interest between compounding dates is credited at the equivalent fractional-period rate; a bank that pays no interest until the next compounding date would credit slightly less.
- Daily compounding uses 365 periods per year; actual/360 or leap-year day counts are not modelled.
- Daily compound interest (IC-4096) is a future tool that will share this compound-growth engine; the Calculator.net Interest Calculator and investment calculators are audited separately.