How this calculator works
Future value (FV) projects what money is worth at a later date after growing at a given rate of return. This calculator covers a lump sum invested today plus an optional periodic contribution added at the end of each month, with your choice of compounding frequency.
The calculation simulates the balance month by month, so contributions and any compounding frequency (annual, quarterly, monthly, or daily) combine correctly rather than relying on a formula that only works for one specific frequency. The year-by-year table breaks the projection into what you contributed and how much came from growth.
The formula
Lump sum only: FV = PV × (1 + r/n)^(n·t)With monthly contributions (monthly compounding): FV = PV(1+i)^m + PMT × ((1+i)^m − 1) ÷ i, where i = r/12 and m = monthsPV is the present value, r the annual rate as a decimal, n compounding periods per year, t years. For compounding frequencies other than monthly, this calculator simulates month by month using an equivalent monthly growth factor.
Worked example: $5,000 + $100/month at 6% for 20 years
- Start with a $5,000 present value, add $100 at the end of every month, 6% annual rate compounded monthly, for 20 years (240 months).
- The lump sum alone would grow to 5,000 × (1 + 0.06/12)^240 ≈ $16,551.02.
- The monthly contributions grow to 100 × ((1 + 0.06/12)^240 − 1) ÷ (0.06/12) ≈ $46,204.09.
- Total future value ≈ $62,755.11, of which $29,000 is contributions ($5,000 lump sum + $24,000 in $100 monthly deposits) and about $33,755 is growth.
Frequently asked questions
What is the difference between future value and compound interest?
They use the same underlying math. Future value is the general term for projecting money forward in time; this calculator frames the inputs around a present value and periodic contributions, useful when thinking about a specific savings or investment target.
Should contributions be at the start or end of the period?
This calculator assumes contributions at the end of each month, which is the standard assumption for salary-based saving. Start-of-period contributions would earn slightly more, since each one gets one additional period of growth.
How does compounding frequency change the result?
More frequent compounding at the same nominal annual rate produces a slightly higher future value, since interest starts earning interest sooner. The difference between daily and annual compounding is usually small at typical interest rates.
How is this related to present value?
Future value and present value are inverse calculations at the same rate and number of periods. Discounting a future value back to today with the present value calculator, then growing it forward again, returns the original amount.
Can I use this calculator for a one-time lump sum with no ongoing contributions?
Yes — enter your lump sum and set the periodic contribution to zero (or leave it blank). The calculator then falls back to the lump-sum-only formula, FV = PV × (1 + r/n)^(n·t), and the year-by-year table shows growth alone with no contribution amounts added in future years.