Forex Lot Size Calculator — Position Sizing by Risk

Account balance$Risk per trade%Stop-losspipsPip value (per standard lot)$

Risk amount$100

Lot size0.5 lots

Units50,000

Standard lot = 100,000 units (≈ $10/pip on USD-quote pairs). Mini = 0.1, micro = 0.01. Pip value varies by pair — verify for yours.

The short answer

Lot size (in standard lots) = (account balance × risk %) ÷ (stop in pips × pip value per standard lot). Risking 1% of a $10,000 account on a 50-pip stop, with a $10/pip standard lot, gives ($100) ÷ (50 × $10) = 0.2 lots — two mini lots. A standard lot is 100,000 units of the base currency; mini is 10,000 and micro is 1,000. Pip value varies by pair, so always confirm it.

The formula: risk first, size second

Correct position sizing works backwards from risk, not forwards from a hunch. The formula is Lot size = (account balance × risk %) ÷ (stop distance in pips × pip value per lot). You decide *how many dollars* you’re willing to lose on the trade (the numerator), divide by *how many dollars you lose per lot if the stop hits* (the denominator), and the result is the number of lots that keeps the loss exactly at your chosen amount.

This is the opposite of how most beginners trade. Instead of picking a lot size and discovering the risk afterwards, you fix the risk — say 1% of the account — and let the math hand you the size. Widen your stop and the size shrinks; tighten it and the size grows, all while the dollars at risk stay constant. That consistency is what survives a losing streak.

Lot sizes: standard, mini, and micro

Forex trades in lots, which are fixed quantities of the base currency. A standard lot is 100,000 units, a mini lot is 10,000 units (0.1 standard), and a micro lot is 1,000 units (0.01 standard). Most platforms accept fractional lots, so a calculator output of 0.2 simply means two mini lots.

The lot size sets the pip value — how much one pip is worth in your account currency. For pairs quoted in USD with a USD account, a standard lot is roughly $10 per pip, a mini lot about $1 per pip, and a micro lot about $0.10 per pip. These are the figures to plug into the formula’s denominator.

Pip value is not always $10 — confirm it

The convenient “$10 per pip per standard lot” only holds cleanly for pairs where the quote currency is USD (the second currency), like EUR/USD or GBP/USD, when your account is in USD. For other pairs, pip value shifts: in USD/JPY the pip value depends on the USD/JPY rate; in a cross like EUR/GBP it depends on the GBP/USD rate to convert back to dollars; and if your account is denominated in euros or pounds, every figure changes again.

Practically, this means you should read the actual pip value from your broker’s platform (most show it per lot for the pair you’re on) rather than assuming $10 everywhere. The calculator is only as accurate as the pip value you feed it — get that right and the lot size is right; guess it and your real risk drifts from your intended risk.

Worked example: 1% risk on a 50-pip stop

You have a $10,000 account and risk 1% per trade, so the dollars at risk are 10,000 × 0.01 = $100. You’re trading EUR/USD with a 50-pip stop, and pip value for a standard lot is $10. Lot size = $100 ÷ (50 × $10) = $100 ÷ $500 = 0.2 standard lots — i.e. two mini lots. If price hits your stop, you lose exactly $100, your planned 1%.

Change one input and watch it flow through: tighten the stop to 25 pips and the size doubles to 0.4 lots (because each lot now risks half as much), while the dollar loss stays $100. Drop the risk to 0.5% and the size halves to 0.1 lots. The dollars at risk are always the thing you hold fixed; the lot size is the output that bends to keep it there.

The risk you actually need to know about

Forex and CFDs are high-risk leveraged products and are not available to US retail traders — in the United States, retail forex is tightly restricted and CFDs are prohibited for retail clients. The majority of retail CFD accounts lose money. Leverage cuts both ways: the same mechanism that lets a small account control a 100,000-unit lot also lets a few bad trades do outsized damage. Position sizing limits the bleeding, but it doesn’t remove the risk.

Where it’s permitted, Vantage is a multi-asset broker offering forex and CFDs with a built-in pip-value/position-size tool on its platforms, which makes feeding the right numbers into this formula straightforward. Confirm eligibility and regulation for your jurisdiction before opening any account. This is educational, not financial advice.

Forex Lot Size Calculator: FAQ

01How do you calculate forex lot size?

Lot size = (account balance × risk %) ÷ (stop distance in pips × pip value per standard lot). You fix the dollars you’re willing to lose, then divide by the dollar loss per lot if the stop is hit. Risking $100 on a 50-pip stop at $10/pip gives 0.2 standard lots — two mini lots.

02What is the difference between standard, mini, and micro lots?

A standard lot is 100,000 units of the base currency, a mini lot is 10,000 units (0.1 standard), and a micro lot is 1,000 units (0.01 standard). For USD-quoted pairs with a USD account, that’s roughly $10, $1 and $0.10 per pip respectively. Smaller lots let you size positions precisely on smaller accounts.

03Is pip value always $10 per standard lot?

No. The clean $10-per-pip figure applies to pairs quoted in USD (like EUR/USD) when your account is in USD. For pairs like USD/JPY, crosses like EUR/GBP, or accounts in other currencies, pip value differs and must be converted. Always read the actual pip value from your broker’s platform rather than assuming $10.

04How much should I risk per forex trade?

Many traders cap risk at 1–2% of account balance per trade so that a losing streak can’t wipe the account. The calculator lets you set whatever percentage you choose and returns the lot size that keeps the dollar loss at that level. Lower risk per trade means smaller drawdowns but slower growth — it’s a personal trade-off.

05Can US traders use a forex lot size calculator?

The math is universal, but retail forex is tightly restricted in the US and CFDs are prohibited for US retail clients, so the brokers and leverage assumed by most forex tools may not be available to you. Forex and CFDs are high-risk leveraged products and the majority of retail CFD accounts lose money. This is not financial advice.