Find how powerful a range hood you need. Enter the stove type, total burner BTUs, cooktop width, whether the hood is on a wall or over an island, and the duct run; the calculator applies common sizing rules, adds duct losses and flags when makeup air is likely required.
Last updated:
Cooktop
Stove type
BTU/h
Add up all burners (and any griddle or grill), e.g. 4 × 15,000 = 60,000.
in
Hood type
Ducting
ft
Kitchen (optional check)
ft
ft
ft
Enter your values to see the result.
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How to use the Range Hood CFM Calculator
Choose the stove type and, for gas, add up the BTU rating of every burner.
Pick the cooktop width and whether the hood is wall-mounted, island or ductless.
Enter the duct run: straight length, number of elbows and caps.
Optionally enter the kitchen size for an air-change check.
Read the recommended CFM, hood width, duct size and makeup air note.
Range hood CFM rules used
Width rule: CFM = cooktop width (ft) × 100 for wall and under-cabinet hoods, × 150 for island hoods.
Gas BTU rule: CFM = total burner output (BTU/h) ÷ 100.
Duct allowance (rule of thumb): + 1 CFM per ft of straight duct, + 25 CFM per 90° elbow, + 40 CFM per transition or cap.
Recommended CFM = the larger of the cooktop rules + duct allowance, rounded up to the next 50 CFM.
Example: a 36 in gas island cooktop with 70,000 BTU/h total. Width rule = 3 × 150 = 450 CFM; BTU rule = 700 CFM. With 10 ft of duct, 2 elbows and 1 cap: 700 + 10 + 50 + 40 = 800 CFM. That is over 400 CFM, so plan for makeup air.
Quick reference by cooktop
Cooktop
Wall hood (electric/induction)
Island hood (electric/induction)
Gas (BTU rule)
24 in
200 CFM
300 CFM
40,000 BTU → 400 CFM
30 in
250 CFM
375 CFM
60,000 BTU → 600 CFM
36 in
300 CFM
450 CFM
75,000 BTU → 750 CFM
48 in
400 CFM
600 CFM
110,000 BTU → 1,100 CFM
60 in
500 CFM
750 CFM
140,000 BTU → 1,400 CFM
Figures before duct allowance. The BTU totals are examples; use your range's actual ratings.
Tips for a range hood that works
Capture beats power. A hood that is deep enough and at least as wide as the cooktop catches more than a stronger, narrower one.
Keep ducts short and straight. Smooth metal duct, few elbows and a direct exit outdoors preserve airflow. Never vent into an attic or wall cavity.
Use the back burners, which sit under the strongest part of most hoods.
Turn the hood on before you start cooking and leave it running a few minutes afterwards.
Clean or replace grease filters regularly; clogged filters cut airflow and are a fire risk.
Frequently asked questions
How many CFM do I need for a range hood?
A common rule is 100 CFM per foot of cooktop width for a wall hood and 150 CFM per foot for an island hood, so a 30 in range needs about 250 CFM on a wall or 375 CFM over an island. For gas, also allow 1 CFM per 100 BTU/h of total burner output and use the larger number.
How many CFM for a gas stove?
Add up all burner ratings and divide by 100. A 4-burner gas range totaling 60,000 BTU/h needs about 600 CFM; a 48 in pro-style range at 110,000 BTU/h needs about 1,100 CFM. Add more for long ducts and elbows.
Why do island range hoods need more CFM?
An island hood has no wall behind the cooktop to guide smoke and steam upward, and cross drafts spread the plume. That is why island hoods are sized at about 150 CFM per foot of width and should be a few inches wider than the cooktop on each side.
When is makeup air required for a range hood?
The International Residential Code (section M1503) requires makeup air for kitchen exhaust hoods capable of more than 400 CFM, supplied at roughly the same rate as the exhaust. Many local codes adopt this; some areas have different rules, so check with your building department.
How do duct length and elbows affect range hood CFM?
Each foot of duct and every fitting adds resistance, so the hood moves less air than its rating. A common rule of thumb adds about 1 CFM per foot of straight duct, 25 CFM for each 90° elbow and around 40 CFM for each transition or wall or roof cap.
Is a higher CFM range hood always better?
Not always. An oversized hood is noisier, uses more energy, may need makeup air and can depressurize the house. Choose a hood that meets the requirement with some margin and has variable speeds, and keep ducts short, smooth and the full size of the hood outlet.
What duct size does a range hood need?
Use the outlet size the hood manufacturer specifies. As a rough guide, hoods up to about 400 CFM often use 6 in round duct, 600–900 CFM hoods 8 in, and 1,200 CFM hoods 10 in. Never reduce the duct below the outlet size.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.