Units = (account × risk%) ÷ |entry − stop|. The liquidation figure is an approximation (entry ÷ leverage from entry, before fees and maintenance margin) and every venue calculates it differently — check your exchange's own formula.
About this calculator. The result is an educational estimate. Contract sizes, pip values, spreads, commissions and overnight financing differ by broker and by instrument, and fills can differ from the prices you model. Check your own account's specification before trading.