Smart Bid Cap is an optimization type that automatically sets and adjusts the maximum bid (Bid Cap) for your ad sets based on actual CPA and spend rate. In Definition Mode, you choose Manual (enter a fixed amount) or Calculator, which calculates the cap as average order value times Margin times Aggressiveness (Conservative uses 50% of breakeven, Moderate 65%, and Aggressive 80%), with a preview of the calculated value on screen. With auto-adjust on, the rules are: if CPA gets close to the cap, the cap goes up to give you a safety margin. If CPA is well below the cap and the ad set is spending, the cap goes down to save money. If the ad set barely spends (underspend), the cap goes up to ensure delivery. Adjustments are capped at 25% at a time, never go below US$1, and each ad set waits 24 hours between adjustments. Bid Cap optimizations don't use weekly distribution by day.