Find your use case: baked batter/icing, glaze, or custard—then choose the substitute that matches the flavor strength you need.
Start with the listed ratio (extract is usually concentrated, so zest/oil needs different measuring).
If using zest or concentrate, fold it in after wet ingredients are combined so it distributes evenly.
If using orange oil or marmalade, begin with the lower end of the ratio and adjust after tasting the batter or sauce.
For best aroma: use zest early (for mixing) and for best citrus “extract feel”: use oil sparingly so it doesn’t overpower.