There's a post on r/Forex that sums up a problem we hear about constantly: "Need help with my lot size on XAUUSD. I have tried online calculators but something is incorrect."
The replies blamed his stop loss input, his account currency, his broker. None of that was the problem.
His calculator wasn't broken and his inputs were fine. The real issue: gold doesn't follow the forex position sizing rules, and most online calculators were built for forex with gold bolted on as an afterthought. Bolted-on support means some calculators get it right, some are off by a factor of 10 — and nothing on the page tells you which one you're using.
30-second answer: One standard lot of XAUUSD = 100 oz. A $1 move in gold = $100 per lot. Lot size = risk amount ÷ (stop distance in dollars × 100). Example: $200 risk, $5 stop → 0.40 lots.
This guide walks through the actual math so you can sanity-check any calculator — or skip them entirely.
Why gold lot sizing is different
In forex, one standard lot is 100,000 units of the base currency. EUR/USD, one lot, 100,000 euros. Industry standard, no ambiguity.
Gold doesn't work that way. One standard lot of XAUUSD is 100 troy ounces — the same size as the <a href="https://www.cmegroup.com/markets/metals/precious/gold.contractSpecs.html" target="_blank" rel="noopener">COMEX gold futures contract</a> (GC, 100 oz). Retail XAUUSD is a CFD or spot contract, so there's no exchange-enforced standard, but most platforms use the 100 oz multiplier.
What that means in practice: for every $1 the gold price moves, one standard lot gains or loses
$1.00 × 100 oz = $100
That's the one number to memorize: $1 of price movement = $100 per lot. Every formula and table below comes from this line. (Same logic as forex, by the way — the lot is measured in the thing you're buying, gold; the P/L lands in the currency it's priced in, dollars.)
Take a gold price of $3,300 as a round example — one standard lot controls $330,000 of notional value, roughly triple a EUR/USD lot. The higher gold goes, the bigger that gap gets. This is why traders who move from forex to gold with the same lot sizes get hurt in the first week.
The formula, in three steps
Lot size = risk amount ÷ (stop distance in dollars × 100)
Step one: set your risk amount. Account balance × risk per trade. A $10,000 account at the commonly used 2% risks $200 per trade.
Step two: set your stop distance — in dollars, not pips. Long from 3,310 with a stop at 3,305? Your stop distance is $5.
Step three: divide. $200 ÷ ($5 × 100) = 0.40 lots.
That's it. No pip value lookup, no leverage anywhere in the formula. Leverage changes your margin requirement, not how many lots you should trade — a distinction we covered in detail in our <a href="/en/classroom/forex-risk-management">risk management guide</a>.
Quick check that the math holds: 0.40 lots × 100 oz = 40 oz. Price drops $5, you lose 40 × $5 = $200. Exactly the risk you set.
Why calculators disagree: gold has three pip definitions
You'll notice the formula above never uses the word "pip." That's deliberate, because gold's pip is where the whole mess starts.
EUR/USD has one universally accepted pip: 0.0001. Gold has no agreed definition at all. Ask three brokers what one pip of gold is and you can get three different answers:
| Convention | 1 pip equals | Value per standard lot | Used by |
|---|---|---|---|
| $0.01 (cent) | a 1-cent move | $1 | many MT4/MT5 platforms with 2-decimal quotes |
| $0.10 (dime) | a 10-cent move | $10 | plenty of calculators and spec sheets |
| $1.00 (dollar) | a full $1 move | $100 | how traders actually talk |
The same $5 stop loss is 500 pips, 50 pips, or "5 bucks" depending on who's counting.
And that's why the Reddit poster's numbers were "incorrect": he was thinking in one convention while his calculator used another. A 10x error in lot size — and if the cent and dollar conventions collide, 100x. That's not a rounding issue. That's the difference between opening 0.04 lots and 0.40 lots, and the bigger one loses money ten times faster.
We learned this one the hard way. An early version of our dynamic position sizing module was developed against a broker quoting gold to two decimals; a live deployment ran on a three-decimal broker, and the same code produced lot sizes 10x apart. Since then we have an internal rule: gold stops are expressed in dollar distance, and the word "pip" doesn't appear in the code.
Our advice to you is the same: skip pips for gold entirely and work in dollar distance. We built our <a href="/en/tools/position-size-calculator/xauusd">XAUUSD lot size calculator</a> around exactly this idea — it accepts both inputs and states its convention right on the page.
One more trap: broker contract specs vary
100 oz is the norm, not a law.
Some brokers offer 10 oz mini gold contracts. Some set gold's minimum lot at 0.10 instead of 0.01. A few offshore platforms use custom multipliers. All of it lives in the contract specification — right-click the symbol in MT4/MT5 and open "Specification."
Thirty seconds before you trade, confirm two things:
- Contract Size = 100. If it isn't, replace the 100 in the formula with whatever your broker uses.
- Minimum volume and lot step. If the formula says 0.04 lots but your platform's minimum step is 0.10, the trade doesn't fit — skip it or widen the setup. Don't round up and hope.
Side note: a broker whose specs are clear and standard tends to be sane in other areas too. It's a decent quick filter when <a href="/en/classroom/how-to-choose-broker">choosing a broker</a>.
Lot size cheat sheet
Pre-calculated for common account sizes and stop distances, all on 100 oz contracts. Fractional results are rounded down to the nearest 0.01 lot — rounding up would push risk past your budget (so 0.0667 becomes 0.06, not 0.07):
| Account | Risk | $3 stop | $5 stop | $10 stop | $20 stop |
|---|---|---|---|---|---|
| $1,000 | 1% ($10) | 0.03 | 0.02 | 0.01 | — |
| $1,000 | 2% ($20) | 0.06 | 0.04 | 0.02 | 0.01 |
| $5,000 | 1% ($50) | 0.16 | 0.10 | 0.05 | 0.02 |
| $5,000 | 2% ($100) | 0.33 | 0.20 | 0.10 | 0.05 |
| $10,000 | 1% ($100) | 0.33 | 0.20 | 0.10 | 0.05 |
| $10,000 | 2% ($200) | 0.66 | 0.40 | 0.20 | 0.10 |
| $100,000 (prop) | 0.5% ($500) | 1.66 | 1.00 | 0.50 | 0.25 |
A "—" means the result is under 0.01 lots: that stop is too wide for that account. Don't force it.
Two notes on using the table:
- Gold's dollar ranges dwarf major forex pairs — multi-dollar swings inside a single session are routine when the market is active (check the current ATR). If you're still setting $2-3 stops out of EUR/USD habit, normal volatility will eat them. Wider stop, smaller lots.
- The $100,000 row uses 0.5% because that account size usually means a prop firm challenge with a 5-10% drawdown limit. Tighter risk buys you more consecutive losses before you're out.
The three mistakes we see most
The first is applying the forex formula as-is. "50-pip stop, $10 per pip, $200 risk, 0.40 lots" works on EUR/USD and falls apart on gold at the very first step — "50 pips" of gold means nothing until you know which convention is in play.
The second is trading a fixed lot size regardless of stop distance. A 0.10 lot with a $3 stop risks $30; the same 0.10 lot with a $20 stop risks $200. Same lot, nearly 7x the risk. Recalculate every trade and keep the dollar risk constant instead.
The third one mostly hurts EA users: running martingale or grid recovery on gold. Doubling down after losses blows up fast on an instrument this volatile — most martingale gold EAs we've tested don't survive a backtest through a single trending stretch like March 2020 or 2024. Our <a href="/en/classroom/how-to-choose-ea">EA selection guide</a> has a checklist for reading an EA's sizing logic, and the <a href="/en/classroom/ea-backtest-guide">backtesting guide</a> covers how to verify it yourself.
Setting lot size in a gold EA
Manual traders can run the formula per trade. If you run EAs, check which sizing mode yours supports:
- Fixed lots: you do the math once with your typical stop distance and enter a conservative value. Downside: risk drifts whenever the stop varies.
- Dynamic risk: the EA computes lot size from account equity and the actual stop of each trade — effectively this article's formula in code. <a href="/en/products">FXTool's EAs</a> all support this mode.
Either way, before going live, run the EA's first trade through the <a href="/en/tools/position-size-calculator/xauusd">XAUUSD lot size calculator</a> and confirm the numbers match. Misconfigured sizing — usually forex parameters copy-pasted onto gold — is one of the most common blown-account causes in our support tickets.
FAQ
How much is a $1 gold move worth on 0.01 lots? 0.01 lots = 1 oz, so a $1 move is $1. A $10 move is $10. Micro lots are the safest way for small accounts to learn gold.
How much margin does one lot of gold require? Notional value ÷ leverage. Example: at $3,300 gold, one lot is $330,000 notional — $3,300 of margin at 1:100, $660 at 1:500 (proportionally more at higher gold prices). Margin determines whether you can open the trade; your stop and risk percentage determine whether you should.
What's the minimum lot size for gold? 0.01 lots (1 oz) on many MT4/MT5 platforms, 0.10 on some. Check Minimal Volume in your broker's contract specification.
Why does my gold stop loss keep getting hit? Probably forex-sized stops. A $2-3 stop on gold often sits inside ordinary intraday noise — price clips it and carries on in your direction. The fix is in the cheat sheet section above: size stops from ATR and shrink lots to match.
Is the calculation the same for silver? Same formula, different contract: one standard lot of XAGUSD is 5,000 oz, so a $0.10 silver move is $500 per lot. Always check the contract spec before switching metals.
The whole thing in five lines
- One standard lot = 100 oz; $1 of price movement = $100 per lot
- Lot size = risk amount ÷ (stop distance in dollars × 100)
- Skip pips — gold has three competing definitions; dollars are unambiguous
- Check your broker's contract spec: Contract Size should say 100
- Recalculate every trade; keep risk constant, not lot size
Or let the tool do it: the <a href="/en/tools/position-size-calculator/xauusd">XAUUSD lot size calculator</a> has these rules built in — account, risk %, stop, done. The companion <a href="/en/tools/pip-calculator/xauusd">XAUUSD pip value calculator</a> shows what each pip is worth at any lot size, in whichever convention your broker uses.
Risk disclosure: Trading forex and precious metals on margin involves leverage and carries a high level of risk, including the possible loss of all deposited funds. This article is an educational walkthrough of position sizing math, not investment advice. The cheat sheet values are formula outputs — always verify against your broker's contract specification.
About the author: The FXTool team builds and tests MetaTrader trading tools daily. We run every EA we sell on live accounts and publish the results. This guide reflects what we've learned from building 50+ EAs and working with thousands of retail traders.