Compound interest calculator with monthly top-ups

Start from a common case

What do you want to know? What I’ll have How much a month How long What rate

Starting amount

Top-up each month

Interest rate a year

Years

Or tap a rate on offer today:

$10,000 to start, $500 a month, 4% a year, over 20 years

$205,613 after 20 years

From year 17, interest adds more each year than you do.
Your first $100,000 takes 11 years 3 months. Your second takes 8 years 5 months.
$100 more a month adds $36,677.

$51k$103k$154k$206k

1 year20 years

20 years: $205,613. You put in $130,000, interest $75,613, $138,372 in today’s money.

You put in Interest In today’s money Interest overtakes top-ups

Show the working

A = P(1 + r/n)^nt + M × ((1 + r/n)^nt − 1) ÷ (r/n)

In Excel or Google Sheets: =FV(4%/12,240,-500,-10000)

Compounding, top-up timing, fees, inflation, rising top-ups

Interest joins the balance

Top-ups arrive

Raise top-ups each year by

A raise you pass on to your savings.

Add once a year

A bonus, added at the end of each year.

Stop top-ups after

0 means never. The money stays and keeps growing.

Yearly fee

Comes off the rate, e.g. a fund’s 0.5%.

Inflation

Singapore’s 10-year average, from SingStat.

Data: each bank’s own website, checked 13 Nov 2026. Full table and method on Numbers.sg