Identify the role xanthan gum played in your recipe: thickening (sauce/batter), suspension (keeping things blended), or gelling (set texture).
Choose the closest option from the list based on heat use and final texture: guar gum (viscosity), psyllium (binding), gelatin (firm set), chia (gel), cornstarch (heat-thickened).
Use the listed ratio as a starting point, then mix in small increments until the texture matches your target.
If your substitute needs hydration (psyllium, chia), let it sit 5–15 minutes, then re-check thickness before adding more.
Do a quick final consistency test: simmer sauces until glossy, and chill gels briefly to confirm set before you commit.