Forex Compounding Calculator: Project Account Growth Month by Month

What this calculator does

This tool projects the future value of a trading account when each month's gain is reinvested and an optional fixed deposit or withdrawal is applied. Instead of assuming a single lump sum grows untouched, it models the realistic case: you trade a percentage return, that profit stays in the account, and you may also top up (or skim off) a fixed amount every month. The output is a balance for every month, plus a breakdown of how much of the final figure came from your own contributions versus pure compounding.

The formula

The engine iterates one simple recurrence, month by month:

balance_next = balance_now × (1 + r) + deposit − withdrawal

where r is your monthly return expressed as a decimal (a 3% month is r = 0.03). Starting from balance_0, the calculator applies this line N times to reach balance_N.

The growth term balance_now × (1 + r) is what makes this compounding rather than simple interest: next month's return is earned on this month's profit too. The + deposit − withdrawal part is applied after the return, so a fresh deposit only starts compounding from the following month. If you set the deposit and withdrawal to zero, the recurrence collapses to the familiar closed form balance_N = balance_0 × (1 + r)^N.

Worked example

Say you start with $10,000, target a 3% monthly return, add a $200 deposit each month, and run it for 12 months.

• Month 1: 10,000 × 1.03 + 200 = $10,500.00
• Month 2: 10,500 × 1.03 + 200 = $11,015.00
• Month 3: 11,015 × 1.03 + 200 = $11,545.45
• ...
• Month 12: $17,096.01

Over the year you contributed $10,000 + (12 × $200) = $12,400 of your own money. The ending balance is $17,096.01, so roughly $4,696 of the total came from compounding the returns rather than from cash you added. That gap is the entire point of reinvesting: the curve bends upward because each month's base is larger than the last.

Reading the curve and avoiding traps

A monthly return % is an assumption, not a promise. The calculator does exactly what you tell it, so a "guaranteed" 10% per month input will show a fantasy number. Real returns are uneven — winning and losing months alternate, and a single bad month scales down everything that follows. Use a return figure you can actually sustain, and consider running the projection twice: once optimistic, once with a return you'd be unhappy but unsurprised to hit.

Compounding cuts both ways. The same recurrence with a negative r shrinks the account just as fast as a positive one grows it. A 50% drawdown needs a 100% gain to recover, which is why the projection is only as honest as your risk control. Pair this tool with a position-size calculator so the monthly return you plug in is backed by a realistic per-trade risk.

Deposit timing matters. This model adds the deposit at month-end, after the return is booked, so that month's deposit earns nothing yet. If your real broker statement credits deposits at the start of the period, your live results will run slightly ahead of the projection. The difference is small over short horizons but compounds over years.

Costs are not modeled here. Spreads, commissions, and overnight swap are already baked into the net return you should be entering — don't plug in a gross strategy return and forget the friction. Tighter trading conditions raise the net r you can realistically sustain: on FXNX, NX Pro's raw spreads from 0.0 pips and transparent commissions keep more of each move in your equity curve, which is exactly the variable this calculator is most sensitive to.

Why traders use it

Compounding projections turn a vague goal ("grow the account") into a testable plan. By adjusting the monthly return, deposit, and horizon until the ending balance matches your target, you back into the discipline the plan actually requires — and you quickly see whether your goal needs a higher return, more capital, or simply more time. Most traders discover that modest, repeatable returns plus consistent deposits beat chasing a heroic monthly number that blows up the account.