Match your recipe goal: for pasta chew, choose semolina (or semolina + all-purpose for smoother dough).
Measure using the listed ratio, then check dough feel: durum-like dough should be firm and slightly tacky, not soupy.
If your substitute is wetter/higher absorption (whole wheat or bread flour), add water gradually 1 tablespoon at a time until cohesive.
Let the dough rest 15–30 minutes before shaping; this improves hydration for blends and helps gluten-free dough set.
If the dough feels elastic but tears (too low structure), switch to bread flour or add semolina next time; if it’s tough, blend in more all-purpose.