Quick answer: Depositing 500 a month for 20 years at 5% on top of 10,000 grows to 232,643.24: 130,000 deposited and 102,643.24 of interest.
How it's calculated
For an ordinary annuity (deposits at the end of each period), FV = D × ((1 + i)^n − 1) ÷ i, where D is the deposit, i the rate per period (annual rate ÷ deposits a year) and n the number of deposits. A starting amount P adds P(1 + i)^n. The rate is treated as a nominal yearly rate compounded with each deposit; if yours is an effective yearly rate, the result is a little lower.
For an annuity due (deposits at the start of each period) the deposit part is multiplied by (1 + i), because every deposit earns one extra period.
This is the saving phase. To see how long a sum lasts once you start drawing an income from it, use the annuity payout calculator.
Worked examples
- 10,000 + 500 a month, 5%, 20 years, ordinary: FV = 232,643.24
- Same as an annuity due: FV = 233,499.56
Frequently asked questions
What is the difference between an ordinary annuity and an annuity due?
The timing. Ordinary: payments at the end of each period (most savings plans and loans). Due: at the start (rent, insurance premiums).
Is this an insurance annuity?
It is the maths behind one. Insurance annuities add fees, guarantees and sometimes variable returns; check the contract's actual rate and charges.
Can I change the frequency?
Yes: monthly, quarterly or yearly. The annual rate is divided by the number of deposits a year.
How do I enter a monthly savings plan?
Choose monthly deposits, enter the amount you'll add each month and the annual rate. The calculator divides the rate by the number of deposits a year.
How much of the final amount is interest?
The result separates what you deposited from the interest. Over long periods, interest can overtake your deposits.
Can I start with nothing saved?
Yes. Enter 0 as the starting amount and the result comes from your deposits alone.