Before you start
Know the total amount you could afford to lose without changing your daily life. Check that you understand the product you plan to trade, including whether it uses borrowed money. Confirm how your provider handles stop orders, which are instructions to close a trade at a set price, since a stop can fill at a different price from the level you see on a chart.
Choose the share of the account at risk
Position sizing starts with a decision about how much of your account you are willing to lose on a single idea. Many investors pick a small, fixed share and do not move above it. Set that share before you look at any chart, because it is easy to change it when a trade feels promising.
Your share at risk is the cash you would lose if the trade moved against you and reached your planned exit. It is not the same as the position size, which is how many units or shares you buy. Keeping those ideas separate stops a strong view from quietly increasing the risk.
Steps to size a trade
Work through the same sequence every time, so the result follows your written plan rather than your mood.
- Write down the share of your account you are prepared to lose on this trade.
- Choose the price where a stop order would close the trade if the market turns against you.
- Measure the stop distance, which is the gap between your entry price and that stop price.
- Divide the cash at risk by the stop distance to find the position size.
- Check that the result fits your account and the trading rules your provider sets.
- Place the trade only if every figure still matches the plan you wrote down.
A wide stop distance produces a smaller position for the same share at risk. Tight stops allow a larger position, yet ordinary price moves reach them more often. Size the trade from a stop you can justify, and never widen it just to keep the position large.
Volatility sizing with average true range
Average true range, usually shortened to ATR, measures how far a market tends to move over a period. It looks at the largest of several price ranges for each period on the chart, then averages them across a chosen window. The result gives you a sense of typical movement rather than a single extreme day.
Some investors place the stop at a multiple of the average true range instead of at a fixed chart level. A widely moving market produces a larger reading, so the stop sits further away and the position shrinks. Quiet markets give a smaller reading, which allows a larger position for the same share at risk. Choose the multiple by testing it on past price data before you rely on it.
Fixed fractional versus fixed ratio
Fixed fractional sizing keeps the share at risk the same on every trade, so the cash amount moves with the account. After a loss the position gets smaller, and after gains it grows.
A fixed ratio method works differently. You trade a set number of units and move up to a larger size only after the account reaches a target you chose in advance. It adjusts more slowly, and it can keep a position large after losses. Neither method removes the chance of losing money, and both depend on the stop being respected.
When losses run past your plan
If a trade keeps reaching its stop, check whether the stop sits inside normal market movement before you change your share at risk. Review the average true range reading for the same period. If the size you calculated does not match the size your provider calculates, stop and recheck the arithmetic. Do not place the trade until the figures agree.
If your losses regularly exceed the share you planned to risk, treat it as a process problem rather than bad luck. Pause new trades and review the plan you wrote down. Your provider's own guidance on order types is the reference to check, and your local financial authority can explain how trading is regulated in your country.
Account features that help with sizing
Position sizing is a habit you bring to any account, but some features make it easier to apply. Check whether an account lets you place stop orders as intended and shows the margin used by each position. Products such as contracts for difference (CFDs) carry a risk of losing money, so the CFD guide is a useful starting point.
Compare how each account handles borrowed funds, using the margin account guide as a checklist. Read the maximum drawdown definition as well, because it explains how a losing streak can shrink an account.
Check the provider's own terms for how its sizing tools and order types work where you live. Define your share at risk before you compare providers.