Identify whether your recipe needs “sharp heat” (cayenne-like bite) or just “warm spice.”
Pick the substitute that matches your goal, then apply the listed substitution ratio.
If the substitute is less hot than cayenne (like smoked paprika), increase gradually in small pinches until the heat level is right.
If the substitute is hotter or more textured (like red pepper flakes), grind first and use a slightly smaller amount, then taste.
Taste after cooking (or during mixing for sauces) and fine-tune with a final pinch so the flavor doesn’t turn bitter or overly smoky.