Identify your use: no-bake crust (needs strong binding) vs. baked crust vs. “cookie crumb” topping.
Choose the closest flavor/texture match from the table (digestive biscuits and vanilla cookies work in most crusts 1:1).
Crush to the same particle size your recipe expects: fine crumbs for tighter crust; chunkier crumbs for topping texture.
Apply the listed ratio, then check consistency: if it looks loose, add 1–2 teaspoons extra fat per cup of crumbs.
Taste and adjust: graham crackers are sweet; add a pinch of salt or a tiny splash of vanilla/lemon to rebalance if needed.