How to Calculate Lot Size in Forex, With Worked Examples for EURUSD, GBPJPY and USDJPY

What is a lot in forex

A lot is a standardized trade size. In retail forex, a standard lot is 100,000 units of the base currency, a mini lot is 10,000 units (0.1 lot), and a micro lot is 1,000 units (0.01 lot). Those conventions are widely used on MetaTrader style platforms. Investopedia's lot definition and BabyPips' lots and leverage lesson cover the same sizes. Always confirm your broker's contract size in the symbol specification before you trade.

The lot number you type in the order ticket multiplies every pip of movement. On EURUSD, 1.0 lot moves about $10 per pip for a USD account. The same 1.0 lot on a JPY pair moves a different dollar amount because the quote currency and the exchange rate change the conversion.

How pip value works for EURUSD, GBPJPY and USDJPY

A pip is the standard price increment traders use for forex. For most pairs quoted to four decimals, one pip is 0.0001. For JPY pairs, one pip is 0.01. BabyPips explains the convention in pips and pipettes, and Investopedia's pip definition matches it. Pipettes are the next digit of precision (0.00001 or 0.001) and do not change the lot formula if you keep stops in whole pips.

For a USD account, pip value per 1.0 lot is:

EURUSD is the clean case. Pip size is 0.0001 and the quote is USD, so for 1.0 lot (100,000 units): 0.0001 × 100,000 = $10 per pip. Mini lots are $1 per pip. Micro lots are $0.10 per pip. You can cross check this on a pip calculator.

USDJPY and GBPJPY quote in yen, so the pip lands in JPY first. Pip size is 0.01, so for 1.0 lot the pip is worth 0.01 × 100,000 = 1,000 JPY. To get USD, divide by the USDJPY rate. Using the European Central Bank reference via Frankfurter on 2026-10-01, USDJPY was 157.98, so 1,000 ÷ 157.98 ≈ $6.33 per pip per 1.0 lot. That rate moves every session, so treat $6.33 as the worked example for that day, not a permanent constant. The USDJPY lots calculator and GBPJPY lots calculator refresh the conversion when you size the trade.

The lot size formula from account risk

Start from how much of the account you are willing to lose if the stop is hit. Convert that into dollars, measure the stop in pips, then divide by the dollar risk of one lot across that stop.

That is the same formula the position size calculator and the pair lots calculators use. Widen the stop and the lot size falls. Raise the risk percent and the lot size rises. Never reverse the order: pick the stop from the chart first, then size the lot to the risk rule. If you pick the lot first, you are guessing, not managing risk.

Worked example: EURUSD lot size

Account equity: $10,000. Risk rule: 1% per trade, so risk money is $100. Setup: long EURUSD with a 50 pip stop. Pip value at 1.0 lot: $10.

• Risk per 1.0 lot: 50 × $10 = $500
• Lot size: $100 ÷ $500 = 0.2 lots
• That is 2 mini lots, or 20 micro lots

Run the same numbers in the EURUSD lots calculator to confirm before you send the order.

Worked example: USDJPY lot size

Same account and risk: $10,000 and 1% ($100). Same 50 pip stop on USDJPY. Using USDJPY at 157.98 (Frankfurter, 2026-10-01), pip value at 1.0 lot is about $6.33.

• Risk per 1.0 lot: 50 × $6.33 ≈ $316.50
• Lot size: $100 ÷ $316.50 ≈ 0.32 lots

Notice the lot size is larger than the EURUSD example for the same dollar risk and the same pip stop. That is because each pip is worth less in USD on USDJPY at this rate. The risk in dollars is still $100 if the stop is hit. Use the USDJPY calculator so you do not hard code a stale rate.

Worked example: GBPJPY lot size

GBPJPY is a cross quoted in yen. For a USD account, the pip still converts through USDJPY the same way as USDJPY itself when the quote is JPY: 1,000 JPY per pip per 1.0 lot, divided by USDJPY. At 157.98 that is again about $6.33 per pip per 1.0 lot.

Keep the same $100 risk and a 50 pip stop:

• Risk per 1.0 lot: 50 × $6.33 ≈ $316.50
• Lot size: $100 ÷ $316.50 ≈ 0.32 lots

Cross pairs can move farther in pips than majors on the same news. If your chart stop needs to be 80 pips instead of 50, recalculate. At $6.33 per pip, an 80 pip stop risks about $506.40 per 1.0 lot, so lot size for $100 risk is about 0.20. The GBPJPY lots calculator and the GBPUSD lots calculator help you compare related dollar and yen expressions of sterling risk.

Common lot sizing mistakes

1. Sizing from conviction instead of the stop. A strong setup does not change the math. Wider stops need smaller lots for the same risk.
2. Using EURUSD pip value on every pair. JPY pairs and crosses convert differently. Recalculate or use the pair calculator.
3. Ignoring account currency. If your account is EUR or GBP, convert pip value into that currency before dividing.
4. Forgetting the risk reward filter. Lot size controls loss size. It does not make a poor target worth taking. Check how to calculate risk reward ratio before you size.
5. Copying someone else's lot size. Their account size, stop, and broker contract may all differ from yours.

Use a calculator so the rate stays current

Hand math is useful for understanding. Live sizing is safer with a tool that applies the current conversion. SIWAI's EURUSD, USDJPY, and GBPJPY pages take account size, risk percent, and stop distance and return the lot size to type into the order ticket. Pair that with the position size calculator when you want the same risk rule on indices or other CFD symbols that use points instead of pips.

If you also trade US index CFDs, remember the SIWAI convention there is $1 per point per 1.0 lot for US30, NAS100, and SPX500. That is a different instrument family from forex lots. See US30 vs NAS100 for index sizing examples.