Forex Compounding Calculator

A forex compounding calculator projects how an account balance grows when each period’s profit is added back to the capital and the next period’s gain is earned on the larger total. The result is a constant-rate projection, not a forecast of what a trading strategy will produce.

What the results show

The calculator reports three figures:

• Future balance: the projected account value at the end of the final period.
• Total contributions: the money you put in yourself, meaning the starting balance plus any additions.
• Interest earned: future balance minus total contributions, the part of the ending value produced by returns, including returns on earlier returns.

Comparing interest earned with total contributions shows how much of the outcome depends on the assumed rate of return and how much depends on your own deposits. When contributions make up most of the future balance, the projection is driven mainly by saving, not by trading performance.

How compounding works

Without reinvestment, growth is linear: the same dollar profit is added each period. With reinvestment, growth is exponential, because every period starts from a larger base.

A simple example: $100 at 10% per year for two years. Year one earns $10, taking the balance to $110. Year two earns 10% of $110, which is $11, so the balance reaches $121 and total profit is $21. Without compounding, each year earns a flat $10, giving $120. The $1 gap is small after two periods and widens with every period added.

The compounding formula

For a starting balance with no additions:

FV = P × (1 + r)^n

• P = starting balance
• r = return per compounding period (as a decimal)
• n = number of periods

If the rate is annual and compounded m times a year, r becomes the annual rate divided by m, and n becomes years multiplied by m.

When a fixed contribution C is added at the end of each period, the contributions grow as a series:

FV = P × (1 + r)^n + C × [((1 + r)^n − 1) ÷ r]

This version assumes deposits arrive at the end of each period. Deposits made at the start of each period earn one extra period of return, which produces a slightly higher figure.

Compounding in forex trading

In a trading account, compounding happens through position size. As the balance grows, a trader who risks a fixed percentage of the account per trade opens larger positions, so the same percentage gain produces larger dollar profits.

That link between balance and position size works in both directions, and a constant-rate projection hides several effects:

• Losses compound too. A 20% drawdown needs a 25% gain to recover. A +10% period followed by a −10% period leaves the account 1% lower, not flat.
• Returns are uneven. Real results vary from period to period, and the order of wins and losses changes the ending balance even when the average return is the same.
• Trading costs reduce the compounding base. Spreads, commissions and overnight swaps are not part of the formula, so enter a return that is already net of costs.
• Lot sizes come in increments. Brokers fill positions in fixed steps (0.01 lots, or 1,000 units, is a common minimum), so small accounts cannot scale position size smoothly with every dollar of profit.
• Withdrawals and taxes reduce the base and are not modeled.

Choosing a compounding frequency

Compounding more often speeds growth only when the per-period rate is converted correctly. A 1% daily return and a 1% monthly return are very different assumptions. As a hypothetical example, 1% compounded over 21 trading days is about 23.2% for the month, and over 252 trading days roughly a 1,127% gain for the year. Sustaining a fixed daily return is far harder than the arithmetic suggests, and daily compounding magnifies any overestimate.

Match the frequency to how often you resize positions. If you recalculate lot size monthly, use a monthly period with a monthly net return.

Using the result

The projection is most useful for testing assumptions, not for setting targets:

1. Start with a net-of-costs return from your own trading history over many trades, or from a backtesting tool if you do not yet have a live record.
2. Run the same balance and period count at a lower rate to see how sensitive the outcome is. Small changes in the per-period rate produce large differences over long horizons.