Calculator inputs
Enter cooktop heat output, then refine with hood and duct details.
Formula used
This tool uses a common planning rule: Base CFM = Total BTU ÷ 100. It then applies multipliers for hood placement, cooking intensity, filter resistance, duct length, elbows, duct size, and cooktop width.
Final estimate: Recommended CFM = clamp(Base CFM × Π multipliers, 150, 1500).
How to use this calculator
- Enter total cooktop output in BTU/h (or select kW for electric ratings).
- Choose hood type and cooking style to match your real habits.
- Add duct length, elbows, and duct diameter to account for pressure losses.
- Press Calculate CFM to see your recommended airflow.
- Use Download CSV or Download PDF for planning notes.
Example data table
| Scenario | Total BTU/h | Hood type | Duct (ft) | Elbows 90 | Duct (in) | Cooking style | Estimated CFM |
|---|---|---|---|---|---|---|---|
| Standard 30" daily cooking | 45,000 | Wall canopy | 10 | 1 | 6 | Medium | ~520 |
| Island cooktop, more smoke | 60,000 | Island canopy | 15 | 2 | 7 | Heavy | ~1,020 |
| Compact apartment setup | 30,000 | Wall canopy | 6 | 0 | 6 | Light | ~250 |
Examples are planning estimates; real performance depends on hood design and installation.