Position Size Calculator – Risk-Based Trade Sizing
Good traders decide the size from the risk, not from the feeling. Tell this calculator your account size, the percent you are willing to lose on one trade, your entry and your stop — it returns the exact quantity and notional value to trade.
Position sizing is the risk-management skill that separates traders who survive from traders who blow up. The maths: risk amount = account × risk percent; position size = risk amount ÷ distance between entry and stop. If your stop is below your entry the calculator reads the trade as a long; above entry, a short. It also shows the notional value of the position and whether you would need leverage to take it, because a correctly-sized trade on a wide stop can still be bigger than your account. Risking 0.5–1% per trade is the range most disciplined traders use; at 1%, you can lose ten trades in a row and still keep about 90% of your account.
How to use it
Enter your account size — the full balance you are trading with, in dollars.
Set your risk — the percent of the account you accept losing if the stop is hit (1% is a sane default).
Add entry and stop — the stop goes where the trade idea is wrong, not where the pain feels acceptable.
Trade the size shown — that quantity loses exactly your chosen risk amount if the stop is hit.
What you get
Exact quantity & notional — units to buy and the dollar value of the position.
Auto direction — long or short is read from entry vs stop.
Leverage check — see whether the sized position needs leverage, and how much.
Works for any market — crypto, forex, stocks: if it has an entry and a stop, it sizes.
Frequently asked questions
How do you calculate position size?
Divide the amount you are willing to lose (account × risk %) by the distance between entry and stop. Example: a $1,000 account risking 1% is $10; with entry $100 and stop $95, size = 10 ÷ 5 = 2 units, a $200 position.
What risk percent should I use?
Beginners often start at 0.5–1% per trade. At 2%+ per trade, a normal losing streak of 8–10 trades costs 15–20% of the account, which is hard to recover from psychologically and mathematically.
Where should the stop go?
At the price that proves the trade idea wrong — beyond the support, resistance or invalidation level you based the trade on — never at a round dollar loss you picked first. Size follows the stop, not the other way round.
Does this work for spot trading?
Yes. With no leverage, the notional simply cannot exceed your account; the calculator flags when the risk-sized position would need leverage so you can widen the plan or skip the trade.