Risk is decided before you enter, not after. Enter your balance, the percentage you accept losing and your stop size — you get the size in lots, along with something other calculators don't give you: your stop as a share of the pair's real daily range, measured from a live terminal.
There is no secret here, and any calculator that hides its formula deserves suspicion:
Lots = (Balance × Risk%) ÷ (Stop in pips × Pip value per lot)
The pip value for one lot is fixed in the quote currency: 10 units per pip on pairs quoted to four decimals, and 1,000 on JPY pairs quoted to two. Converting that into your account currency is the only step that needs a rate, which is why we ask for it outright instead of guessing it.
Thirty pips on EURGBP (median range 23 pips) is a stop wider than a whole day. The same thirty on GBPNZD (range 123) is a stop that noise will hit. A fixed number means your risk varies without you knowing it.
A fixed size with a variable stop = a variable loss. Fixing the amount at risk is what makes your results readable, because every trade becomes the same unit of measurement.
If you open a full currency basket, you pay the spread seven times. Our measured average per leg is 12.8 points (roughly 1.3 pips) — size the whole basket, not a single leg.
The result is before spread, commission and swap. Check the current spread cost, because it changes by the hour and blows out around the news.
Position size = the amount you accept losing ÷ (stop size in pips × pip value per lot). If your balance is $5,000 and you risk 1%, that is $50; with a 25-pip stop on a pair whose pip is worth $10 per lot, position size = 50 ÷ (25 × 10) = 0.2 lots.
The common range among traders is 1% to 2% of capital per trade. The figure itself is not a sacred rule, but keeping it constant is what makes a losing streak survivable: ten losses in a row at 1% cut the balance by about 10%; at 10% they cut it by about 65%.
No. A 30-pip stop is wide on a pair whose median daily range is 23 pips and very tight on one whose range is 123. A stop is measured against the pair's usual movement, which is why this calculator shows your stop as a share of each pair's measured median daily range.
Other tools. Pip value calculator · Forex liquidity and spreads