Divide before multiply

Severity: Med ID: divide-before-multiply

Flags arithmetic expressions where division is performed before multiplication, which can cause unintended precision loss in integer arithmetic.

What it does

Warns on expressions of the form (a / b) * c (or equivalent shapes), where the integer division truncates before the result is multiplied.

Why is this bad?

Solidity's integer division truncates toward zero. Performing (a / b) * c discards the remainder of a / b before scaling, while (a * c) / b preserves precision. This pattern frequently manifests as fee/share/yield miscalculations.

Example

Bad

uint256 share = (amount / total) * weight; // truncates first, then scales

Good

uint256 share = (amount * weight) / total; // preserves precision