Position Size Calculator

How position sizing protects your account

This free position size calculator helps forex, crypto and stock traders work out how many units to trade. It is for anyone who wants to risk a fixed amount on each trade. It runs entirely in your browser, needs no sign-up, and stores nothing. You enter your account size, risk percent, entry price and stop loss, and it returns the position size that keeps your loss at your chosen risk.

What is position size in trading?

Position size is the number of units, shares or lots you buy or sell in one trade. It decides how much you gain or lose when price moves. A larger position means a larger profit when you are right and a larger loss when you are wrong. Traders set size from the risk they accept, never from a guess.

Position size is the single most important risk control in trading. Two traders can take the same trade idea, and the one with the smaller, correctly sized position survives a losing run while the other does not. That is why sizing comes before entry timing in most professional risk plans.

How is position size calculated?

First work out your risk amount by multiplying your account size by your risk percent. Then measure the stop distance, which is the gap between your entry price and your stop loss. Finally divide the risk amount by the stop distance. The answer is your position size in units. Divide that by 100,000 to get forex lots.

Worked example: a $10,000 account risking 1 percent risks $100. With an entry at 1.1000 and a stop at 1.0950, the stop distance is 0.0050. Dividing $100 by 0.0050 gives 20,000 units, which is 0.20 standard lots. At 50 pips of stop distance and a pip value of $10 per standard lot, that position also risks $100, which confirms the maths.

The foreign exchange market is enormous. The Bank for International Settlements reported in its 2025 Triennial Survey that average daily turnover in global foreign exchange markets reached $9.6 trillion in April 2025. In a market that large, disciplined sizing matters far more than any single trade idea.

Why should you risk only 1 percent per trade?

Risking 1 percent per trade means ten losing trades cost about 10 percent of your account, not half of it. That leaves capital and confidence to keep trading. Many professionals risk 1 percent or less because it keeps losses small while winners can still grow the account. Bigger risk turns ordinary losing streaks into serious damage.

The maths of losses is unforgiving. Lose 50 percent of an account and you need a 100 percent gain just to get back to where you started. Lose 10 percent and you need only about 11 percent to recover. Small, fixed risk keeps every drawdown recoverable.

What does leverage change about position size?

Leverage does not change the position size that matches your risk. It changes the margin, which is the deposit your broker holds to open the trade. With 10 to 1 leverage, a $22,000 position needs $2,200 of margin. Higher leverage lets you open bigger positions with less cash, which also means losses can grow faster.

Leverage is often misunderstood as a way to make more money. It only changes how much capital you must deposit. Your profit and loss still depend on position size and price movement, so a leveraged position sized badly loses money just as fast as an unleveraged one.

How do you use the stop loss with this calculator?

Place your stop loss where your trade idea is wrong, at a support level, a recent low, or beyond normal price noise. Then enter that price here and let the calculator set the size. Never move the stop further away to fit a bigger position. If the stop distance is wide, the correct size is simply smaller.

Always set the stop first, then size the trade. Traders who pick a position size first and then squeeze the stop to fit it usually place stops where price noise, not logic, will hit them. The stop belongs where the idea fails, and the size follows from that distance.