You need roughly 100 CFM for every 10,000 BTUs of your stove's total output.
For general effectiveness, multiply your kitchen's volume (Width x Depth x Height) by 10 to find the minimum extraction rate needed per hour. Which Cooker Hood? Buying Guide - Bosch buy kitchen hood
To capture all fumes, your hood must be at least as wide as your cooktop. A 30" cooktop needs at least a 30" hood. You need roughly 100 CFM for every 10,000
Because they face cross-drafts, they should always be wider than the cooktop (extend 3–6" beyond the range). 3. Calculate Required Power (CFM) Power is measured in CFM (Cubic Feet per Minute) or buy kitchen hood
Aim for 100 CFM per linear foot of cooktop width.