What pip value is and why it matters
A pip is the standard minimum price move (0.0001 on most pairs; 0.01 on yen pairs). The pip value is how much money your account gains or loses per pip the price moves — and it depends on the instrument and your position size.
Why it's the key piece: all your risk is calculated with it. Loss = stop-loss pips × pip value. If your stop is 20 pips away and each pip is $10, you risk $200. Without knowing pip value you can't translate "my stop gets hit" into "I lose $X", and therefore can't size the position properly. That's why this calculator feeds directly into the position size and real cost tools.
The easy rule: for USD-quoted pairs with a USD account, a standard lot (100,000 units) is always $10/pip, a mini lot $1/pip and a micro lot $0.10/pip. For pairs where USD is the base (USD/JPY…) or gold, the value changes with price, which is why we mark them approximate.