What Size Range Hood Do I Need? A Simple Sizing Method
What size range hood do I need? The short answer: at least as wide as your cooktop, ideally 3 inches wider on each side, with enough CFM to match your burners. That’s two numbers, width and airflow. Most people get the width roughly right, then badly undersize the airflow. Honestly, the airflow is the part that decides whether your kitchen actually clears. Width is easy. Airflow is where it goes wrong. So this guide gives you the exact method: nail the width, then calculate the CFM from how you cook, and let your mounting type settle the rest.
Last updated: August 11, 2026. CFM and clearance figures verified.
The Two Numbers That Decide Hood Size
- Width — must cover the cooktop; wider captures more of the plume.
- CFM (airflow) — must match your burner output and how hard you cook.
Everything else (depth, mounting height, ducted vs ductless) adjusts these two. Get both right and the hood works. Get width right but CFM wrong and you’ve bought a good-looking fan that leaves a greasy film. Trust me, I’ve seen that mistake far more than the reverse.
Step 1: Size the Width to Your Cooktop
Your hood should never be narrower than your cooktop. Standard widths are 30, 36, and 48 inches. The baseline:
- 30-inch cooktop → 30-inch hood minimum
- 36-inch cooktop → 36-inch hood minimum
- 48-inch cooktop → 48-inch hood minimum
Here’s the upgrade most people skip: go 3 inches wider on each side where you can, because cooking vapor spreads outward as it rises. A 36-inch cooktop is better served by a 42-inch hood, especially if you sear or wok-cook. In practice the extra width costs little and captures the edges a flush-width hood misses. Honestly, it’s the cheapest performance upgrade on the whole spec sheet.
Step 2: Calculate the CFM From How You Cook
CFM (cubic feet per minute) is the airflow, and it’s where sizing goes wrong. Two ways to find your number, use the higher one:
By burner output (the one that matters most): divide your total BTUs by 100. A 36-inch gas range at 60,000 BTUs needs about 600 CFM. For electric or induction, roughly 100 CFM per 10,000 BTU-equivalent, which usually lands lower.
By kitchen volume: length × width × height = cubic feet, then × 15 air changes ÷ 60 for heavy cooking (× 10 for light). A 10×10×8 kitchen (800 cu ft) at 15 changes needs about 200 CFM. It turns out this number is almost always lower than the burner number, which is why I lean on the burners.
Use whichever is higher. Always the higher one. I’d recommend leaning to the burner math for gas, because that’s your real worst-case. If you’re deciding by cooking style rather than doing math, our kitchen vent hood ideas guide breaks CFM down by how you cook.
The code trap: any hood over 400 CFM needs a makeup-air system under the International Residential Code (M1503.6), because a sealed house can’t feed that much exhaust. Don’t buy 900 CFM you can’t legally supply air to.
Step 3: Let Your Mounting Type Fine-Tune It
If it’s a wall-mounted hood, width and CFM as calculated. Depth runs about 20 inches; it vents straight up and is the most forgiving.
If it’s an under-cabinet hood, width must fit the cabinet opening above the range, and depth is capped by the cabinet (usually 18 to 20 inches). Match the cooktop width and confirm the gap; our under-cabinet range hood ideas guide covers the fit gotchas.
If it’s an island hood, size up, and don’t skimp here. Open-room cross-drafts scatter the plume, so go wider (42 inches over a 36-inch cooktop) and add roughly 50 percent more CFM than a wall install. Most people undersize island hoods, and it’s the setup I see disappoint owners most.
Step 4: Mount It at the Right Height
Height isn’t a size, but it changes how much size you need. Manufacturers specify 24 to 30 inches above electric cooktops and 30 to 36 inches above gas (more heat). Too low is a fire and clearance risk; too high and even a strong fan loses the plume, forcing you to oversize CFM to compensate. Follow the manual. If you have to mount high, buy more airflow.
Decision Matrix
| Cooktop | Cooking style | Width | CFM target |
|---|---|---|---|
| 30-inch electric | Light | 30 in | 300–400 |
| 30-inch gas | Moderate | 30–36 in | 400–600 |
| 36-inch gas | Heavy / wok | 42 in | 600–900 (+ makeup air) |
| 48-inch gas range | Any | 48–54 in | 900–1200 (+ makeup air) |
| Island, 36-inch | Any | 42 in | ~50% above wall figure |
| No duct (recirculating) | Light–moderate | match cooktop | as high as the model offers |
When to Bring in a Pro
Get a contractor involved when your CFM crosses 400 (makeup air), when a new duct run goes through joists or the roof, or when a combustion appliance sits nearby. Undersizing risks a smoky kitchen; oversizing without makeup air risks backdrafting the water heater, which is a carbon monoxide problem, not a comfort one. Once you know your size, our best range hoods for gas stoves roundup lists models by width and CFM.
Frequently Asked Questions
What size range hood do I need for a 30-inch stove?
A 30-inch hood at minimum, and a 36-inch hood captures the edges better if your layout allows. For airflow, plan on 300 to 400 CFM for light electric cooking and 400 to 600 CFM if it’s gas or you cook with high heat often.
Should a range hood be bigger than the cooktop?
Ideally yes. Going 3 inches wider on each side catches the vapor that spreads outward as it rises, which a flush-width hood lets escape onto your cabinets. It matters most over islands and for high-heat cooking; it’s optional for light cooks in tight kitchens.
How many CFM do I need for a gas range?
Divide your total burner BTUs by 100. A 60,000 BTU range wants about 600 CFM. Remember that any hood above 400 CFM legally requires a makeup-air system, so very high CFM adds installation cost.
Does a ductless range hood need to be a different size?
Match the same width to your cooktop. Ductless models recirculate rather than exhaust, so choose the highest CFM the model offers to offset the efficiency lost to charcoal filters. Width capture still follows the cooktop.