Investment Calculator

Every amount you invest grows by the yearly return for as long as it stays invested. Your starting amount grows for the whole time; each contribution grows from the day it goes in. Growth is then added to the balance and grows too, which is why the growth part gets bigger every year. These results are illustrations from a steady return you choose. Real investments rise and fall, and nothing here is a prediction or advice.

The formula

monthly growth = (1 + yearly return)^(1 ÷ 12)
starting amount grows to = start × (1 + yearly return)^years
monthly contributions grow to = contribution × (monthly growth^months − 1) ÷ (monthly growth − 1)
end balance = the two added together
with fees: yearly growth = (1 + return) × (1 − fee)
with tax: end balance − tax rate × (end balance − total put in)
today's money = end balance ÷ (1 + inflation)^years

Worked example

Start with 10,000, add 500 at the end of every month and assume 7% a year for 20 years. The starting amount grows to 10,000 × 1.07²⁰ = 10,000 × 3.8697 = 38,697. The monthly growth is 1.07^1/12 = 1.005654, so the 240 contributions grow to 500 × (3.8697 − 1) ÷ 0.005654 = 253,768. The end balance is 38,697 + 253,768 = 292,465. You put in 10,000 + 500 × 240 = 130,000, so 162,465 of it is growth.

Fees, tax and inflation

• Fees. A 0.5% yearly fee makes the yearly growth 1.07 × 0.995 = 1.06465, and the end balance falls to 273,875. That is 18,590 lost to fees, more than the 130,000 put in × 0.5% × 20 years would suggest, because the fee also comes out of your growth.
• Tax. With a 15% tax on gains at the end, the tax is 15% × 162,465 = 24,370, leaving 268,095. Real tax rules depend on your country and the type of account, so this is a rough guide.
• Inflation. At 3% a year, 292,465 in 20 years buys about what 292,465 ÷ 1.03²⁰ = 161,931 buys today.

The rule of 72

Divide 72 by the yearly return (after fees) to estimate how long money takes to double: 72 ÷ 7 ≈ 10.3 years. The exact figure is log 2 ÷ log 1.07 = 10.24 years.

Example returns

The conservative (4%), moderate (7%) and aggressive (10%) buttons are only example assumptions so you can see a range. On the default inputs they end at about 203,832, 292,465 and 426,405. They are not forecasts for any investment.

Related calculators

For savings interest at any compounding use the compound interest calculator. To find the yearly growth rate between two values use the CAGR calculator. To plan income after work use the retirement calculator, and for Indian mutual fund SIPs use the SIP calculator.

Assumes the same return every year, with contributions monthly or yearly as you choose and any step-up applied every 12 months. Fees are taken from the balance a little each month. Results are illustrations only.