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Compounding Calculator

Grow a balance one period at a time. Add a regular contribution and a periodic drawdown to see how much of the curve survives a realistic run of bad periods.

Inputs

Negative numbers are allowed.
0 for none. Applied after the period's return.
0 for never.

Results

Compounding summary
Final balance after 12 months$12,682.42
Total growth
Relative to the starting balance, contributions included.
+26.82%
Total gains from returns+$2,682.42
Total contributed$0.00
Total lost to drawdowns$0.00

Balance chart

 1 |################################         $10,200
 2 |#################################        $10,404
 3 |#################################        $10,612
 4 |##################################       $10,824
 5 |###################################      $11,041
 6 |####################################     $11,262
 7 |####################################     $11,487
 8 |#####################################    $11,717
 9 |######################################   $11,951
10 |######################################   $12,190
11 |#######################################  $12,434
12 |######################################## $12,682

By month

Balance by period
monthOpeningReturnContributionDrawdownClosing
1$10,000.00+$200.00$0.00—$10,200.00
2$10,200.00+$204.00$0.00—$10,404.00
3$10,404.00+$208.08$0.00—$10,612.08
4$10,612.08+$212.24$0.00—$10,824.32
5$10,824.32+$216.49$0.00—$11,040.81
6$11,040.81+$220.82$0.00—$11,261.62
7$11,261.62+$225.23$0.00—$11,486.86
8$11,486.86+$229.74$0.00—$11,716.59
9$11,716.59+$234.33$0.00—$11,950.93
10$11,950.93+$239.02$0.00—$12,189.94
11$12,189.94+$243.80$0.00—$12,433.74
12$12,433.74+$248.67$0.00—$12,682.42
Every input is in the URL, so anyone opening this link sees the same numbers.
Compounding against a flat returnTwo account balances over fifteen years at the same yearly rate: one curve bends upwards as gains are left in, the other rises in a straight line.ACCOUNT VALUE$10k$20k$30k$40k051015YEARSCOMPOUNDED 10% a yearSIMPLE: 10% of the original sumboth start at $10,000 and run 15 years$41,772DIFFERENCE$16,772$25,000
Compounding against a flat return. Two accounts start at $10,000 and earn 10% a year for fifteen years. Leaving the gains in means each year earns on a larger balance, so the curve bends away from the straight line and ends $16,772 higher.
How it's calculated
The table caps at 120 rows and the text chart samples 24 evenly spaced periods; the final balance always uses every period.
Formulas used by this tool
Gain per periodopening × return% / 100, or the fixed dollar return
After gainmax(0, opening + gain + contribution)
Drawdownafter gain × drawdown% / 100, only on periods divisible by drawdownEvery
Closingafter gain − drawdown; becomes next period's opening
Growth(final − start) / start × 100

Educational only, not financial advice. The maths is simple arithmetic on the numbers you enter; it knows nothing about your broker, fees, slippage or the market. Questions about the maths? Ask in the forums.