Investment Calculator

Project your investment growth, or solve for the contribution, rate, starting amount, or time needed to reach a goal.

About the Investment Calculator

Project how a starting amount and regular contributions grow under compound interest — or flip it around and solve for the contribution, return rate, starting amount, or time needed to hit a savings goal.

How the Investment Calculator works

Most investment calculators only run in one direction: enter your numbers, get an end amount. This one has five tabs so you can solve for whichever variable you don't know yet. "End Amount" works forward like a typical projection. The other four tabs work backward from a goal: "Additional Contribution" tells you how much you'd need to add regularly, "Return Rate" tells you what growth rate you'd need, "Starting Amount" tells you what lump sum you'd need today, and "Investment Length" tells you how long it would take — all to reach the same target End Amount.

How to use the Investment Calculator

Choose a tab for the value you want to solve for — the other four become your known inputs.
Enter your starting amount, investment length, return rate, and compounding frequency as applicable.
Enter an additional contribution amount, and whether it's contributed monthly or yearly, at the beginning or end of each period.
On any tab other than "End Amount", enter your target End Amount goal instead.
Press Calculate to see the solved value, the balance breakdown, and the full accumulation schedule.

Tips for the Investment Calculator

More frequent compounding (e.g. daily vs. annually) grows a balance slightly faster for the same nominal rate.

Formula used by the Investment Calculator

Future Value = Starting Amount × (1 + i)ⁿ + Contribution × [(1 + i)ⁿ − 1] / i
where i = the periodic growth rate implied by the compounding frequency, n = number of periods

The "Return Rate" and "Investment Length" tabs solve this in reverse using bisection; "Additional Contribution" and "Starting Amount" solve it directly since both terms are linear.

Example: Investment Calculator

Projecting 20 years of investing $5,000 plus $200/month

Starting amount: $5,000
Monthly contribution: $200 (end of month)
Annual return: 7% (illustrative), compounded monthly
Length: 20 years

Result: Ending balance ≈ $124,379.03 ($5,000 starting + $48,000 in contributions + ≈ $71,379.03 growth)

Compounding the starting amount and adding each month's $200 contribution at a monthly rate of 7% ÷ 12 over 240 months produces an ending balance of about $124,379: the $5,000 start plus $48,000 in total contributions (200 × 240 months) plus roughly $71,379 in investment growth.