TryBuildCalcKitchen Exhaust Fan Calculator (Range Hood CFM Sizing)
Size your kitchen exhaust fan instantly.
🕒 Last updated: September 12, 2026
Inputs
ℹ️Measured at the actual cooking surface (burners/elements), not the cabinet width.
ℹ️Island hoods need more CFM per linear foot — no wall to help contain the rising plume.
ℹ️The linear-foot method applies the same rate to gas and electric — gas can need more CFM only when its BTU output is high enough to exceed that.
Required Range Hood CFM
200 CFM
Linear-foot method (see below)
Range & Hood
Cooktop width: 24 in
Hood mount: Wall-Mounted
Fuel type: Electric
Sizing Method Used
Linear-foot method: 200 CFM
Required (linear-foot method): 200 CFM
Assumptions Used
Two independently-sourced sizing methods apply and, when both are computed, the HIGHER is used: the linear-foot method (HVI/Broan guidance — 100 CFM per linear foot of cooktop width for a wall-mounted hood, 150 CFM per linear foot for an island hood, since an island hood has no wall to help contain the rising plume, applied the SAME way regardless of fuel type) and — for gas cooktops with a BTU rating entered — the BTU method (Broan guidance — roughly 100 CFM per 10,000 BTU of total gas output, i.e. BTU ÷ 100). For an electric range, or a gas range with no BTU entered, only the linear-foot method is computed. Broan's own guidance treats the width-based method as reliable for gas cooktops up to roughly 60,000 BTU total output — above that, the BTU method should govern, so a high-output gas range left without a BTU entry can understate the true requirement; a warning is shown above when this applies. Broan also recommends adding CFM beyond these two methods for an integrated grill/griddle or a mounting height above the standard 30in, which this calculator does not model (see Limitations). Range hood CFM is NOT standardized into a common retail size ladder the way bathroom fans are — ratings are continuous and manufacturer-specific across a wide range, so this reports the REQUIRED CFM directly, rounded UP for readability (never down, so the displayed figure never understates the raw requirement). Once the RAW required CFM exceeds 400, IRC M1503.6 MAY require makeup air — but only when qualifying non-direct-vent, non-mechanically-drafted fuel-burning appliances are inside the home's air barrier (an all-electric home is not automatically subject to this), and code tests your INSTALLED system's actual capacity, not this calculator's estimate; code also permits either mechanical or passive makeup air. This is a planning estimate — actual duct length, elbow count, and filter type all reduce a hood's delivered CFM below its rated CFM; confirm your chosen unit's actual performance and your specific appliances/local code requirements with a licensed contractor.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Exhaust Fan / Range Hood CFM Calculator.
Kitchen exhaust fan sizing
A kitchen exhaust fan (range hood) is sized the same way regardless of what you call it — from cooktop width, mount type, and fuel type, using the higher of the linear-foot method and (for gas) the BTU-based method.
This page defaults to a compact 24 in wall-mounted electric cooktop — edit the inputs above to match your actual kitchen.
Exhaust Fan / Range Hood CFM Formula: How Is It Determined?
Bathroom mode selects ONE sizing method based on room size and ventilation type, per HVI's own guidance — it does not compare methods and take the highest. Kitchen mode compares two independently-sourced methods and uses the higher.
Bathroom Mode
Intermittent, ≤100 sq ft: Raw CFM = max(Bathroom Sq Ft × 1 CFM/sq ft, 50 CFM code minimum)
Intermittent, >100 sq ft: Raw CFM = max(Fixture Method, 50 CFM code minimum)
Fixture Method = 50 (toilet) + 50 (if separate shower) + 50 (if standard tub) or 100 (if jetted tub)
Continuous (any size): Raw CFM = 20 CFM flat
Nominal Fan Size = next standard retail size ≥ Raw CFM, up to 300 CFM
Per HVI's own guidance, the square-footage and fixture-based methods are BOTH intermittent-ventilation rules of thumb, and are alternatives selected by room size — not two methods to compare and take the higher of. A jetted/whirlpool tub counts as one fixture (100 CFM), not an addition on top of a separate standard tub. Continuous ventilation is a flat 20 CFM code-compliant rate, not scaled by room size or fixtures. The raw requirement is rounded UP to a standard retail bathroom fan size (50, 80, 100, 110, 150, 190, 250, or 300 CFM), since bathroom fans genuinely are sold in this common size range across manufacturers (though exact model availability still varies by brand).
Kitchen Mode
Linear-Foot Method = (Width in inches ÷ 12) × 100 (wall) or × 150 (island)
BTU Method (gas only, if entered) = Total BTU Output ÷ 100
Required CFM = max(Linear-Foot Method, BTU Method) when BTU is entered for gas, otherwise Linear-Foot Method alone
Required CFM is reported directly, rounded UP for readability (never down, so the displayed figure never understates the raw requirement), since range hood CFM is NOT standardized into a common retail size ladder the way bathroom fans are. Once the RAW required CFM exceeds 400, IRC M1503.6 may require makeup air — but only when qualifying non-direct-vent, non-mechanically-drafted fuel-burning appliances are inside the home's air barrier; code permits mechanical or passive makeup air, sized to your installed system's actual capacity, not just this estimate. Broan's own guidance treats the linear-foot method as reliable for gas cooktops only up to roughly 60,000 BTU total output — above that, entering the BTU rating is necessary, since a width-only estimate can significantly understate a high-output gas range's true requirement. Broan also recommends additional CFM beyond both methods here for an integrated grill/griddle or a mounting height above the standard ~30in, which this calculator does not model.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value |
|---|---|
| Cooktop width | 24 in |
| Hood mount / fuel | Wall-Mounted / Electric |
Comparing Sizing Methods
| Method | Calculation | Result |
|---|---|---|
| Linear-foot | (24/12) × 100 | 200 CFM |
| Required (linear-foot method) | 200 CFM | |
Therefore, this 24 in wall-mounted electric range needs a hood rated at approximately 200 CFM.
Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.