Monthly Compound Interest Calculator

Enter your monthly compounding plan

Your inputs are calculated only in this browser and are never sent to or stored on a server.

A monthly return and an annual return mean different things. Choose which one you are entering first.

How to enter the return
USD

The amount you are starting with. Enter 0 if you are starting from nothing.

%

Converted so that 12 months compound back to this figure. For 10% a year enter 10. Values above -100% and up to 500% are accepted. The result differs from simply dividing the annual return by 12.

pp

Leave this blank to keep a single result. Enter a value to also see the same plan with the annual return lowered by that much (conservative), left unchanged (base) and raised by that much (optimistic).

months

How many months to run, as a whole number. One year is 12, and up to 1,200 months (100 years) is accepted.

Adding every month puts the money in once a month, after that month’s return has been applied. Choosing no contribution removes the amount field below and leaves it out of the calculation entirely.

The example values are a hypothetical illustration of how the calculation works, not a recommended return. Reset example puts those values back; Clear sets every field to 0 and turns the monthly contribution off.

Final balance

$11,000.00

An informational estimate of $10,000.00 run for 12 months at annual return 10%. No monthly contribution was included.

Monthly return applied
0.797414%
Annual return entered (before conversion)
10.0000%
Total contributed
$10,000.00
Estimated gain
$1,000.00
Cumulative return
10.00%
Number of contributions
0

The annual return of 10% was not divided by 12. It was converted with (1 + annual rate)1/12 − 1 to a monthly rate of 0.797414%, so twelve of those months compound back to exactly the annual figure you entered.

The return is assumed to be the same for the whole period. Taxes, fees, inflation, exchange rates and real-world swings in return are not included, and no tax rate or fee rate is ever guessed. This does not guarantee any return and is not investment, legal or tax advice.

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Calculator address: https://calceno.com/en/monthly-compound-interest-calculator

Yearly breakdown

Shows the start and every 12 months. When the period does not divide evenly into years, the final month is added as one more row. For 30 months, the last row is the 2 years 6 months point.

Scroll the table sideways to see every value.

Elapsed time in years and months, elapsed months, total contributed, estimated gain or loss and balance
Elapsed timeMonthsTotal contributedEstimated gain or lossBalance
Start0$10,000.00$0.00$10,000.00
1 year12$10,000.00$1,000.00$11,000.00

Monthly breakdown

Shows every single month from the start (month 0) to the last one. With the current settings that is 13 rows, which you can scroll through inside the table.

Scroll the table sideways to see every value.

Total contributed, estimated gain or loss and balance for each elapsed month
MonthsTotal contributedEstimated gain or lossBalance
0$10,000.00$0.00$10,000.00
1$10,000.00$79.74$10,079.74
2$10,000.00$160.12$10,160.12
3$10,000.00$241.14$10,241.14
4$10,000.00$322.80$10,322.80
5$10,000.00$405.12$10,405.12
6$10,000.00$488.09$10,488.09
7$10,000.00$571.72$10,571.72
8$10,000.00$656.02$10,656.02
9$10,000.00$740.99$10,740.99
10$10,000.00$826.65$10,826.65
11$10,000.00$912.98$10,912.98
12$10,000.00$1,000.00$11,000.00

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