Monthly Compounding Calculator

Monthly Compound Interest Calculator

Calculate growth where interest is compounded monthly, one of the most common ways to model savings and investment growth.

Inputs

Your calculation

Currency

Starting amount

Interest rate

Rate convention

AER/APY already includes compounding. The selected compounding frequency applies only to a nominal rate.

Years

Months

Compounding frequency

Regular contributions

Deposit amount

Frequency

Withdrawal amount

Frequency

Timing

Annual increase

Adjust for inflation

Inflation rate

% annually

Include tax / fees

Tax on interest

Annual fee

Calculation assumptions

Calculations use monthly steps. Weekly payments are averaged as 52/12 payments per month; they are not scheduled by calendar date. Annual payments occur at the beginning or end of each year. Daily compounding uses a fixed 365-day convention. Annual payment increases apply every 12 months to both deposits and withdrawals. Tax applies monthly to positive interest; fees are deducted monthly from the balance and capped at available funds. Withdrawals cannot overdraw the account. Simple interest accrues on contributed capital remaining in the account; withdrawals and fees reduce that capital proportionally. Inflation changes purchasing power, not the nominal balance. Full method.

Outputs

Results

Enter your numbers and click calculate.

Final balance

£0.00

Total contributions

£0.00

Withdrawals: £0.00

Gross interest

£0.00

Tax/fees: £0.00

Year-by-year table

A yearly summary of balance, contributions and interest.

Year	Deposits	Withdrawals	Interest	Tax / fees	End balance

What if I allow five more years?

Calculate to see the comparison.

Simple vs compound interest

Calculate to see the comparison.

Excel formula

A matching FV formula is available for constant monthly payments without tax, fees or account exhaustion. Annual and increasing payments require the exported schedule. Inflation adjustment is separate.

=FV(...)

Growth chart

Compare your balance, net cash paid in and net growth or loss after deductions. Negative returns remain visible.

Yearly chart

Month-by-month table

Click a year to expand the monthly breakdown.

Guide

Monthly compounding and monthly cash flows

£10,000 at a 5% nominal annual rate compounded monthly for ten years becomes approximately £16,470.09 without additional payments. Deposits at the beginning of each month earn that month’s interest; deposits at the end start earning in the next month.

Choose Effective annual rate if the return you have is an AER or APY. For payment examples, see compound interest with monthly deposits.

How this calculator works

Monthly compounding splits the annual rate into 12 compounding periods. It is a useful default for many savings and investment examples because results are easy to compare against regular monthly deposits.

You can still change every input: currency, interest rate, years and months, compounding frequency, contribution timing, inflation and tax or fees. Use the share URL button to save a pre-filled version of the result.

FAQ