Position size calculator
Work out exactly how many units, lots or contracts to trade so you risk only the percentage of your account you choose per trade.
By the TradingCalculator.Pro team · Updated on · About us
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Formula
Size = (Capital × Risk%) ÷ Stop distanceHow it works
Position size comes out of a division, not a hunch: the money you are willing to lose divided by what you lose per unit if the stop is hit. Everything else — the pair, the broker, the leverage on offer — only enters to translate that second figure into your instrument’s units.
The order matters, and most people do it backwards. First you decide where the stop goes, because the chart dictates that; then how much you risk, which you dictate; and the size is the consequence of both. Picking the size first and fitting the stop around it afterwards is the most common way to blow up an account that had a working system.
What you get
- Always risk a fixed, controlled % (1-2%)
- Stocks, forex, crypto, indices and futures
- Avoids the #1 account killer: overleverage
Worked example
A $10,000 account risking 1% per trade. Long EUR/USD at 1.0850 with the stop at 1.0813, just below the prior swing low.
- Risk in money: $10,000 × 1% = $100.
- Stop distance: 1.0850 − 1.0813 = 0.0037, that is 37 pips.
- Pip value on a standard EUR/USD lot with a dollar account: $10.
- Risk per lot: 37 pips × $10 = $370.
Size = $100 ÷ $370 = 0.27 lots (27,000 units).
Always round down. At 0.27 lots you risk $99.90, inside plan; at 0.28 you risk $103.60, which is 3.6% more than you decided. It looks like nothing on one trade, and it is the difference between following your plan and approximating it, three hundred times over.
The right order: stop, risk, size
Almost everybody sizes backwards, and the way to spot it is to ask what gets decided first. If the answer is "how many lots am I putting on", the stop ends up wherever that quantity fits, and at that point it is no longer where the chart asked for it. A stop that exists to make the size work protects nothing: it only guarantees you get taken out earlier.
The order that works has three steps and none of them is negotiable. First the stop, because price structure dictates it: the prior low, the other side of the range, the invalidation of the pattern. Second the money risk, which you dictate and which should be the same percentage on every trade. And third the size, which is no longer a decision but a division.
The practical consequence of doing it this way is that size changes on every trade, and by a lot. With $100 of risk, a 37-pip stop allows 0.27 lots and a 12-pip stop allows 0.83: three times more. Anyone trading the same size every time is risking three times more on some trades than on others without having decided to, and that unplanned variance is what turns an ordinary losing streak into a hole.
The same formula in every market
The only thing that changes from one instrument to another is how the stop distance translates into money per unit. The division is always the same: money risk divided by risk per unit.
| Market | What a unit is | Risk per unit | Example |
|---|---|---|---|
| Forex | 1 lot = 100,000 of the base currency | pips × pip value | 37 pips × $10 = $370 per lot |
| Gold (XAU/USD) | 1 lot = 100 ounces | $ per ounce × 100 | 8.50 × 100 = $850 per lot |
| Indices (CFD) | 1 contract ≈ $1 per point | points × point value | 90 points × $1 = $90 per contract |
| Stocks | 1 share | price difference | $3.50 per share |
| Futures (ES) | multiplier $50 per point | ticks × tick value | 34 ticks × $12.50 = $425 per contract |
Look at the right-hand column: the amounts run from $3.50 to $850 per unit. That is why the size that comes out is so different in each market, and why copying the lot count from a forex trade to a futures trade multiplies the risk by a factor nobody has worked out.
What an R is, and why it is worth measuring in R
An R is your risk per trade taken as the unit. If you risk $100 and make $250, you have made 2.5R; if you lose what you planned to, you have lost 1R. Measuring this way has an advantage that does not show until the account grows: it makes trades of different sizes, different markets and different months comparable.
It also makes visible what an account in dollars hides. A record that reads "+$1,200, −$800, +$300" says nothing about the system; the same record in R — "+2.4R, −1.0R, +0.6R" — says the winners are bigger than the losers and by how much. Expectancy is computed on that column, not on the dollars.
And there is a detail the product itself honours as a rule: a trade without a stop has no R. It is not zero, it is undefined. Recording it as zero drags the average down and distorts the distribution, which is precisely what you were trying to measure.
How to use it
- Enter your inputs: the terms of the formula (capital, risk, prices and stop).
- The calculator applies the formula and returns the result in your instrument's units.
- Check the breakdown before trading: anything that cannot be computed is shown empty, never as zero.
Frequently asked questions
How do you calculate position size for EUR/USD?
Divide your money risk by the stop distance times the pip value. With $100 of risk, a 37-pip stop and a $10 pip value per standard lot, you get 0.27 lots. Pip value on EUR/USD is fixed at $10 per standard lot for a dollar account because the dollar is the quote currency; on pairs where it is not, such as EUR/GBP, it has to be converted.
What percentage should I risk per trade?
Between 0.5% and 2% of the account, and closer to 1% the less track record you have. The reason is not abstract prudence: at 2% per trade, eight losses in a row leave you 14.9% down and still able to trade normally; at 5%, those same eight losses are 33.7% and you need a 51% gain just to get back to flat.
Does leverage change the position size?
No. Leverage only decides how much margin the broker holds, not how much you lose if the stop is hit. Your loss is always stop distance × size, and size was already fixed by your risk. What leverage does do is let you open a position so large that the correct stop no longer fits in your account — that is where it hurts.
How does the calculation change for stocks or gold?
Only the translation into units changes, never the formula. On stocks the risk per unit is the price difference in dollars per share; on XAU/USD it is the difference per ounce, and a standard lot is 100 ounces. With $125 of risk and an $8.50 per-ounce stop you get 0.147 lots, which most brokers round to 0.14.
What if the result is below my broker’s minimum size?
It means the trade does not fit in your account, and the correct answer is not to take it. This is the most ignored signal there is: raising the risk so the micro-lot "fits" turns a 1% trade into a 3% one without looking like it. The legitimate alternative is to find an entry with a tighter stop, not a wider risk.