What this calculator answers
This page works out how large a trade can be if hitting the stop-loss should cost a fixed share of the account or a fixed amount. You enter the account size and the risk per trade, either as a percentage of the account or, under Advanced options, as a money amount. Depending on the market, you also enter either an entry and a stop-loss price (stocks and crypto) or a stop-loss distance in pips with the pip value per standard lot (forex).
The results are:
- Position size: the number of shares, crypto units or standard lots, rounded down.
- Amount at risk: what the trade loses if it closes at the stop-loss.
- Risk budget: the most you set out to lose, before the size is rounded down.
- Actual risk: the amount at risk as a percentage of the account. Because the size is rounded down, it can be a little below the risk you set, but never above it.
- Risk per share, Risk per unit or Risk per standard lot: the loss on one share, one crypto unit or one standard lot at the stop.
- Position value (stocks and crypto): the size times the entry price.
- Units, Mini lots and Micro lots (forex): the same size counted in units of the base currency and in the two smaller lot sizes.
The formula
The risk budget R is the account size A times the risk per trade r, or the amount typed in Amount to risk. For stocks and crypto, the stop distance d is the gap between the entry price E and the stop-loss price S, whichever side the stop is on, so a short trade is sized like a long one. The size N is the risk budget divided by that distance; for crypto it is kept to six decimal places, which is what the 10⁶ factors do. For forex, the size in standard lots L is the risk budget divided by the stop in pips p times the pip value per standard lot v. The amount at risk X is the size times the distance, or for forex the lots times the pips times the pip value, and the position value V is the size times the entry price. The actual risk q is the amount at risk divided by the account size. In forex, U is the size in units of the base currency.
R = A·r (or the amount entered), d = |E − S|, N = ⌊R / d⌋ (shares), N = ⌊R / d × 10⁶⌋ / 10⁶ (crypto), L = ⌊R / (p·v) × 100⌋ / 100, X = N·d or L·p·v, V = N·E, q = X / A, U = L × 100,000
The brackets ⌊ ⌋ mean rounding down. Shares are rounded down to whole shares, crypto units to six decimal places and forex lots to steps of 0.01, so the amount at risk never exceeds the risk budget.
Worked examples
A stock. Take an account of 10,000 and a risk of 1% per trade on a stock bought at 50 with a stop-loss at 48. The risk per share is $2.00, the gap between the entry and the stop. The position size is 50 shares, with a position value of $2,500.00. If the price falls to the stop, the amount at risk is $100.00, an actual risk of 1% of the account.
Forex. Take the same account and risk, a stop-loss of 50 pips and a pip value of 10 per standard lot. The risk per standard lot is $500.00, so the position size is 0.2 standard lots and the amount at risk is $100.00, an actual risk of 1%. That size is 20,000 units, which is 2 mini lots or 20 micro lots.
A money amount. With the risk entered as a money amount of 250, the same stock trade at 50 with a stop at 48 gives 125 shares. The amount at risk is $250.00, an actual risk of 2.5% of the 10,000 account.
When no position fits
If the risk budget cannot cover one share, one crypto step of 0.000001 unit or 0.01 lot at the chosen stop, the position size is 0. The page then says “No position fits this risk budget at this stop distance.” instead of a sentence to buy, and a warning names the smallest size for that market.
What the result does not include
The calculation assumes the position is closed exactly at the stop-loss price. Slippage, an opening gap past the stop and trading fees are not included, so a real loss can be larger than the planned amount.
The pip value is entered, not looked up; the pip value calculator works it out for your pair and account. Lot sizes follow the standard lot of 100,000 units, the mini lot of 10,000 and the micro lot of 1,000.
FAQ
Can I lose more than the amount at risk?
Yes. Slippage, a price gap through the stop or fees can make the real loss larger than the amount at risk.
Where does the pip value come from?
You enter it, per standard lot and in your account currency, and the pip value calculator on this site works it out. When the US dollar is the second currency in the pair (EUR/USD), a standard lot of 100,000 units moves about $10 per pip. For USD/CHF or USD/CAD it is about $10 divided by the exchange rate, and for USD/JPY, where the pip is 0.01, about $1,000 divided by the rate (roughly $6.67 at 150). Check the figure with your broker.
Does the calculator account for leverage or margin?
No. It sizes the position from the risk budget and the stop distance only. For stocks and crypto it shows a warning when the position is worth more than the account, because such a position would need margin or leverage. Forex mode has no such warning, because it does not model leverage or margin, so check your broker's margin requirement for the lots shown.
What risk percentage per trade do traders use?
There is no single right figure. It depends on the account, the strategy and how many losses in a row a trader can bear. This page's examples use small percentages only to show the arithmetic.
Why does position sizing matter?
It sets in advance how much a trade loses if it reaches the stop-loss, whatever the distance to the stop. For the same loss, a wider stop gives a smaller position and a tighter stop a larger one.
Should the size be the same for every trade?
With a fixed risk per trade, the size changes with the stop distance and the account size. Keeping the size fixed instead makes the amount at risk change from trade to trade.