Skip to content
CalculatorBuddy

Investment Calculator

Solve any one variable of an investment plan — end balance, required contribution, return rate, starting amount, or length — with a full accumulation schedule and balance breakdown.

$
years
%
$
Contribute
At the

of each contribution period. Beginning-of-period deposits earn one extra period of interest.

End Balance

$198,290.40

Starting Amount
$20,000.00
Total Contributions
$120,000.00
Total Interest
$58,290.40

Balance breakdown

Starting amount 10%, Contributions 61%, Interest 29%
  • Starting amount10%
  • Contributions61%
  • Interest29%

Accumulation schedule

PeriodDepositInterestEnding Balance
Year 1$32,000.00$1,526.53$33,526.53
Year 2$12,000.00$2,338.12$47,864.65
Year 3$12,000.00$3,198.41$63,063.06
Year 4$12,000.00$4,110.31$79,173.37
Year 5$12,000.00$5,076.93$96,250.30
Year 6$12,000.00$6,101.55$114,351.84
Year 7$12,000.00$7,187.64$133,539.48
Year 8$12,000.00$8,338.90$153,878.38
Year 9$12,000.00$9,559.23$175,437.61
Year 10$12,000.00$10,852.79$198,290.40
End Balance$198,290.40View results

Plan an investment around whichever variable you don't yet know. Enter your starting amount, return rate, contributions, and time horizon — then pick a tab to solve for the End Balance, the contribution required, the return rate required, the starting amount required, or how long it takes to reach a target. Every result comes with a balance breakdown and a full accumulation schedule.

Formula

The balance grows each period and each contribution is added at the period's start or end. For a starting amount P, a per-period rate i, M periods, and a contribution C added at the end of each period:

End balance = P × (1 + i)^M  +  C × [ (1 + i)^M − 1 ] / i

The per-period rate i comes from your nominal return rate R: first the effective annual rate for the compounding frequency, EAR = (1 + R/n)^n − 1, then the per-deposit rate i = (1 + EAR)^(1/p) − 1 for p deposits per year (12 monthly, 1 yearly).

Because the end balance is a straight-line function of the starting amount and the contribution, those two solve instantly; the return rate and the length are found by search, since the balance only ever rises as either increases.

What each tab solves for

TabYou provideIt solves for
End Amountstart, rate, contribution, lengththe final balance
Contributionstart, rate, length, targetthe contribution needed
Return Ratestart, contribution, length, targetthe rate needed
Starting Amountrate, contribution, length, targetthe start needed
Invest Lengthstart, rate, contribution, targetthe time needed

Examples

$20,000 start · 6% · $1,000/month · 10 years

Starting with $20,000 and adding $1,000 at the end of every month for 10 years at a 6% return (compounded annually) grows to $198,290.40. Of that, $20,000 is your starting amount, $120,000 is contributions, and $58,290.40 is interest.

How much must I contribute to reach $300,000?

Same start, rate, and 10-year horizon, but targeting $300,000: the calculator's Contribution tab solves the required monthly deposit — far quicker than guessing.

Frequently asked questions

What can this investment calculator solve for?
Five things, one per tab. Fill in everything you know and the calculator solves the one you leave out: the End Balance, the Additional Contribution you'd need, the Return Rate required, the Starting Amount required, or how long (Invest Length) it takes to reach a target balance.
How are contributions and compounding combined?
The annual return is converted to the effective rate for your chosen compounding frequency, then to a per-deposit rate at your contribution cadence. So each monthly or yearly deposit earns its fair share of growth. Beginning-of-period deposits earn one extra period of interest versus end-of-period deposits.
What is the difference between this and the interest calculator?
They share the same compound-growth engine. The interest calculator always solves for the ending balance and adds tax and inflation adjustments. The investment calculator can solve for any one of five variables, which is handy for goal planning — "how much must I contribute" or "what return do I need" to hit a target.
Does a higher compounding frequency increase my balance?
Slightly. More frequent compounding raises the effective annual rate a little, so daily or continuous compounding beats annual compounding at the same nominal rate — but the gap is small, and contributions usually matter far more than compounding frequency.
Are investment returns guaranteed?
No. This tool assumes a single, constant return rate, which is a planning simplification. Real returns vary year to year and can be negative. Treat the result as an estimate, not a promise, and revisit it as your actual returns come in.

Related calculators