How much do you need to invest per month?

• You invest the same amount at the end of every month, and every dollar keeps compounding until retirement — the standard future value of an annuity.
• Returns compound monthly. The monthly rate is (1 + annual)^1/12 − 1, so 10% a year really means 10% a year (about 0.797% a month), not 10% ÷ 12.
• Anything you've already invested grows at the same rate for the whole period and is subtracted from what your monthly contributions have to cover.
• The return is assumed to be steady every year. Real markets are not — they go up and down, and the order of those years changes the outcome.
• No taxes, fees, employer match, or contribution limits are modelled, and contributions never increase with your pay.
• The start-age table assumes a clean start from zero at each age, aiming at the same amount by the same retirement age.
• With “today's money” on, your target is grown by inflation to retirement age, so the amount you accumulate has the buying power you asked for. Otherwise the target is taken as a plain future dollar amount.

This is an estimate for planning, not financial advice. Your numbers never leave your browser — nothing you type here is stored, sent, or tracked. Want to know what you could actually invest each month? Deco tracks your real spending automatically.