Future Value Calculator: Lump Sum + Monthly
Use this future value calculator to project what an investment will be worth — a lump sum, monthly contributions, or both. Calculate future value at any rate using the same FV-of-annuity formula every retirement model uses.
$
$
%
yrs
Future value$0
Total contributed$0
Investment growth$0
Growth multiple1.0×
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How this calculator works
This combines two future-value formulas: lump sum compounding plus an ordinary annuity (end-of-month contributions).
FV = PV(1 + m)n + PMT × [((1 + m)n − 1) / m]
- m
- Monthly rate = (1 + annual)1/12 − 1
- n
- Number of months (years × 12)
- PV
- Present (lump-sum) value
- PMT
- Monthly contribution
Use a real (inflation-adjusted) return, typically 5–7% for stocks long-term, to keep the answer in today's purchasing power. Use a nominal return (8–10%) only if you also plan to inflate your future expenses.
Source: Standard FV-of-annuity-due formula. Long-term equity returns — Federal Reserve historical data.
FAQ
Why does my answer differ from a calculator that says 'beginning of month'?
This tool assumes end-of-month contributions (ordinary annuity). 'Annuity due' (beginning-of-month) earns one extra month of compounding per contribution, raising FV by ~0.5–0.6% over long periods. The difference is small but real — most retirement contributions happen mid-month from payroll, splitting the difference.
Should I use 7% or 10% for the rate?
It depends on whether you want a 'today's dollars' answer or a 'future dollars' answer. 7% is the long-term S&P real (post-inflation) return. 10% is the nominal return. Use 7% if you want the answer to feel meaningful in today's spending power; use 10% if you also plan to inflate your spending estimates.
What is the future value formula?
FV = PV × (1+r)n + PMT × ((1+r)n − 1) / r. PV = starting amount, PMT = recurring contribution, r = periodic interest rate, n = periods. The first half compounds a lump sum; the second compounds ongoing deposits.
How is future value used in retirement planning?
It is the foundation of retirement planning. Calculate the FV of your current balance + ongoing contributions at an assumed return (typically 5-7% real) over the years until retirement. Compare to your target (typically 25× annual spending). If FV >= target, you are on pace.
Should I use real or nominal returns for future value?
Real return (inflation-adjusted) gives you the answer in today's dollars — most useful for planning. The S&P 500 long-term real return is ~7%; nominal is ~10%. Stick to real unless you are explicitly inflating future expenses.
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