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Trading calculator
Position Size Calculator and Lot Size Calculator
A position size calculator, also called a lot size calculator in forex, sizes a trade so the loss at your stop stays within the risk you choose. The risk amount is the account balance times the risk percentage. The lot size is that amount divided by the stop distance in pips times the value of one pip per standard lot.
In brief
What the position size and lot size calculator does
Estimate how many forex lots or stock shares fit a risk amount you choose, with the formula shown and its limits stated.
Key takeaways
- Position size follows from the loss you accept at the stop. It does not follow from how confident you feel about a trade.
- Forex lots use pip value per standard lot. Stock shares use the gap between entry price and stop price.
- Results are rounded down to your broker's lot step or to whole shares, so the planned loss stays within the risk amount.
- The calculator is arithmetic. It does not predict outcomes and it does not include spreads, commissions, financing or slippage.
Calculator
Position size and lot size calculator
Formula used
- Risk amount = account balance × risk % ÷ 100
- Forex lots = risk amount ÷ (stop distance in pips × pip value per standard lot)
- Stock shares = risk amount ÷ (entry price − stop price), ignoring the sign
Formula version 2026-11-07. Results are estimates before spreads, commissions, financing and slippage.
About 10 for EUR/USD in a USD account. Use the forex pip calculator for other pairs.
Smallest lot increment your broker accepts, often 0.01.
- Position size (lots)
- 0.25
- Amount at risk
- 100.00
- Loss at stop with rounded size
- 100.00
- Units (at 100,000 per standard lot)
- 25,000
Sizes are rounded down so the planned loss at the stop stays within your risk amount. Gaps, slippage, spreads, commissions and financing can make a real loss larger. Nothing you enter is sent to a server.
How to use the lot size calculator
Start in the forex mode. It needs five inputs, and each one changes the result in a predictable way.
Enter every money value in your account currency. If your account is in euros, use euros for the balance and for the pip value. The calculator does not convert currencies for you.
- 01
Account balance
The equity you are willing to size against, in your account currency. For the same risk percentage, a larger balance gives a larger risk amount and so a larger lot size.
- 02
Risk per trade (%)
The share of the balance you accept losing if the stop-loss is hit. The calculator multiplies the balance by this percentage to get the risk amount. It does not suggest a value.
- 03
Stop-loss distance (pips)
How far price must move against you, in pips, before your planned exit. A wider stop means fewer lots for the same risk amount. Place the stop where your trade idea says it belongs, then measure the distance.
- 04
Pip value per standard lot
What one pip is worth on one standard lot, in your account currency. For EUR/USD in a US dollar account this is about US$10. Other pairs and account currencies differ, so check them with the forex pip calculator.
- 05
Broker lot step
The smallest lot increment your broker accepts, often 0.01. The calculator rounds the lot size down to this step. Read your broker's contract specification, because the minimum and step can differ by instrument.
The result panel shows the lot size, the amount at risk and the loss at the stop with the rounded size. The loss at the stop is the figure that matches the size you will actually trade. The formula article explains each step in more depth.
Worked lot size examples
The three examples below all use EUR/USD in a US dollar account, where one pip on one standard lot is worth US$10. They are illustrative arithmetic, not forecasts or recommendations, and the calculator returns the same figures when given the same inputs.
| Example | Risk amount | Lots (rounded down) | Loss at stop with rounded lots |
|---|---|---|---|
| US$5,000 account, 1% risk, 25-pip stop, EUR/USD | US$50 | 0.20 | US$50 |
| US$10,000 account, 1% risk, 40-pip stop, EUR/USD | US$100 | 0.25 | US$100 |
| US$25,000 account, 0.5% risk, 30-pip stop, EUR/USD | US$125 | 0.41 | US$123 |
The third row's unrounded size is 0.4167 lots. Rounding down to 0.01 gives 0.41 lots, so the planned loss at the stop is US$123 rather than the US$125 risk amount.
For the same risk amount, a narrower stop gives a larger lot size and a wider stop gives a smaller one.
Standard, mini and micro lots
Lot names are market conventions, and each broker defines its own contract sizes. Pairs quoted with fewer decimals, such as many yen pairs, use a different pip size, so check the pair first. For a deeper look at pip size, read what is a pip.
| Lot type | Units of base currency | Pip value for EUR/USD in USD (arithmetic) |
|---|---|---|
| Standard lot | 100,000 | About US$10 |
| Mini lot | 10,000 | About US$1 |
| Micro lot | 1,000 | About US$0.10 |
Pip value equals pip size times units, so 0.0001 multiplied by 100,000 gives US$10. Your broker's instrument specification is the reference, not this table.
Position size calculator for stock shares
Stock mode works differently. There is no pip. The risk per share is the gap between your entry price and your stop price. The calculator divides the risk amount by that gap and rounds down to whole shares. It takes the absolute gap, so a short trade with a stop above the entry works the same way.
Worked example (illustrative): a US$10,000 account, 1% risk, entry at US$50 and stop at US$48. The risk amount is US$100. The gap is US$2 per share, and US$100 divided by US$2 is 50 shares. The position value at entry is 50 multiplied by US$50, which is US$2,500. The planned loss at the stop is 50 multiplied by US$2, which is US$100.
The position value is not the amount at risk. Gaps, fees or a stop that fills below its level can make the real loss larger than US$100.
Why the calculator rounds down
Rounding up can make the planned loss larger than the risk amount you chose, so the calculator rounds down: to your broker's lot step for forex, and to whole shares for stocks.
In the third worked example, the unrounded size is 0.4167 lots. Rounding to 0.42 would put the loss at a 30-pip stop at about US$126, which is above the US$125 risk amount. Rounding down to 0.41 keeps the planned loss at US$123.
What the calculator does not do
- It does not predict outcomes. A correctly sized trade can still lose, reach its target or stay open for longer than you expect.
- It does not include costs. Spreads, commissions, swap or financing charges and slippage sit outside the arithmetic.
- It does not convert currencies. You enter the pip value in your account currency, and the result is in that currency too.
- It does not choose your risk percentage or your stop. Those are decisions you make before you size the trade, not outputs the calculator produces.
Choosing a risk percentage is a personal decision
This page does not recommend a risk percentage. The right figure depends on your balance, income, tolerance for loss and experience.
Some educational material discusses small, fixed percentages of the account per trade. That is a convention to research, not a rule this calculator enforces. Enter the figure you choose deliberately, not after a win or a loss.
Leverage and margin rules differ by country
Position size and leverage are separate questions. Your broker's leverage and margin rules can limit how large a position you may open, and those rules depend on where you live and which regulator oversees your broker.
- In the EU, ESMA introduced retail CFD leverage limits in 2018 as temporary EU-wide measures: from 30:1 for major currency pairs down to 2:1 for cryptocurrencies, with close-out when funds fall to 50% of the minimum required margin. Check ESMA's current publications and your national regulator for the rules that apply today.
- In the US, FINRA replaced the pattern day trader rule and its US$25,000 minimum with intraday margin standards effective 4 June 2026. Brokers can phase the change in until 20 October 2027 and may set stricter house rules. The SEC approved the amendments. For margin accounts, FINRA's day trading page still describes a minimum of US$2,000 in equity.
- Elsewhere, check your regulator's current rules and your broker's product disclosure before you size a position.
For how day trading is structured, read day trading explained. These rules limit how much you can trade; the sizing arithmetic on this page still applies.
Risk disclosure
- Losses can exceed the planned amount. Gaps, slippage, spreads, commissions and financing can make the real loss at a stop larger than the calculator shows.
- Leverage magnifies losses as well as gains. The CFTC and NASAA describe off-exchange forex trading by retail investors as extremely risky, and they warn that losses can wipe out a down payment quickly.
- Margin trading can lose more than the original investment. FINRA's guidance on margin accounts says so directly.
- A correct calculation is not a trading plan. Read risk management guidance and test your method on a demo account before you trade a live account.
RTX5 and this calculator
RTX5 is Orrnn's trading terminal and broker-technology product. Its Windows desktop client is in preview, and the web and mobile clients are planned. A Google Play listing for Android is published, but the mobile client has no approved release record yet; check the product-availability record and release notes before relying on any RTX5 feature. This calculator is an educational page on the RTX5 website, and it is not a trading service.
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Primary references
Sources were checked on 7 November 2026. They explain market rules and concepts; they do not certify RTX5 or provide individual financial advice.
FINRA: Day trading (investor page)Says margin accounts must keep a minimum of US$2,000 in equity and that margin trading can lose more than the original investment. The page is dated 4 June 2026. It does not cover the pattern day trader rule.FINRA Regulatory Notice 26-10 (20 April 2026): Rule 4210 intraday margin standardsSets out the amendments that replace the pattern day trader requirements and US$25,000 minimum with intraday margin standards. Effective 4 June 2026, with firms able to phase in implementation until 20 October 2027.Federal Register: FINRA Rule 4210 amendments (order of 14 April 2026)The SEC order approving FINRA's amendments. It removes the pattern day trader designation and its US$25,000 minimum equity, and replaces them with intraday margin standards. Published 17 April 2026.ESMA: final product intervention measures on CFDs and binary options (1 June 2018)Sets retail CFD leverage limits by asset class, a close-out at 50% of minimum required margin, and per-account negative balance protection. This page does not confirm the measures' current status.CFTC and NASAA investor alert: foreign exchange currency fraudDescribes off-exchange forex trading by retail investors as extremely risky, and warns that losses can wipe out a down payment quickly. The page shows no date.RTX5 product availabilityThe RTX5 status register. Check it before relying on any RTX5 feature.
Questions readers ask
Does a position size calculator predict whether a trade will win?
No. It only does arithmetic on the inputs you enter. It cannot tell you whether price will reach your entry, target or stop, and it does not measure the quality of your analysis. A correct size limits the planned loss only if the stop fills at the planned level. Gaps and slippage can make the real loss larger.
How do I find pip value for other pairs?
Pip value depends on the pair, the lot size and the account currency. Use the forex pip calculator to work out the value of a pip for a pair in your account currency, then enter that figure here as pip value per standard lot. Check your broker's contract specification too.
Is a lot size calculator the same as a position size calculator?
In forex, the two usually mean the same thing: the number of lots you trade so that a stop-loss hit loses a chosen amount. For stocks, the output is a share count. In both cases the risk amount is divided by the loss per unit. Only the unit of size changes.
Why is the planned loss smaller than my risk amount?
Because the lot size is rounded down to your broker's lot step, or the share count to whole shares. In the third worked example the risk amount is US$125, but 0.41 lots lose US$123 at a 30-pip stop. The difference comes from rounding, not from a fee or a profit.
Does the calculator include spreads and commissions?
No. The arithmetic uses only the stop distance and pip value you enter. Spreads, commissions, swap or financing charges, and slippage can all add to a real loss. Include them in your own plan, and check your broker's cost schedule before you trade.
Keep learning
Forex pip calculatorWork out the value of a pip for a pair in your account currency before you size a trade.What is a pipPip definitions, decimal places and how they change the value of a position.Position sizing formula in forexThe longer article on the formula, with more examples and the reasoning behind each step.Risk managementRead the risk framing before you size a live trade.Day trading explainedHow day trading works and the account rules that can apply to it.