Basics
The units price moves in, and what each one is worth in money.
Outcome
Risks US$100.00 of the US$100.00 you planned (1% of the account)
Sizes are rounded down, so a full stop-out never loses more than you planned. Slippage on the stop can still add to it. Contract sizes vary between brokers, especially on metals; check your platform's symbol specification.
The lot size and risk calculator on its own page, with the formulas →
A pip is the standard unit for forex prices: the fourth decimal place for most pairs (0.0001 on EURUSD), or the second for yen pairs (0.01 on USDJPY). Many brokers show a fifth decimal, a 'pipette', which is a tenth of a pip.
Futures move in ticks, the smallest price step a contract allows. On the Nasdaq contracts a tick is 0.25 index points: worth $5 on NQ and $0.50 on the micro MNQ, so a full point is $20 and $2. On the S&P contracts a tick is also 0.25: $12.50 on ES and $1.25 on MES. Indices and gold are usually quoted in points.
For education only, not financial advice.