Design Anatomy

Custom Range Hood Sizing Guide and Printable Spec Sheet

Warm-white clay-plaster custom range hood with an oak ledge over a gas range, with labels pointing out the stainless insert, width, ducting, height, and ledge. — Tap a note to jump to that part.

You can build a stunning architectural feature that actually clears the air by using our printable Custom Range Hood Sizing Sheet to calculate your exact hood width, mounting height, CFM, and framed box dimensions.

Start With the Stainless Liner Insert

Before building anything, you absolutely must purchase the mechanical insert because its specific dimensions dictate your entire framing structure.

Looking up into a custom range hood showing a stainless steel liner insert with baffle filters and integrated lighting. — Baffle filters catch grease better than standard mesh options.

Having the physical unit on hand ensures your wooden skeleton is perfectly sized to hold the stainless liner insert without any frustrating modifications later.

Calculate the Minimum Airflow

Your insert needs enough power to handle your specific cooktop, which is measured in cubic feet per minute or CFM.

Total Gas BTUs	Electric Range Size	Minimum Recommended CFM
Up to 40,000	30-inch standard	400 CFM
40,000 – 60,000	36-inch standard	600 CFM
60,000 – 90,000	36-inch pro-style	900 CFM
90,000+	48-inch pro-style	1200 CFM

Size the Box Six Inches Wider

Design the hood to be exactly 6 inches wider than your cooking surface to create a truly functional capture area.

Front view of a plaster range hood extending slightly wider than the stainless steel gas range below it. — An overhang captures steam that naturally billows outward.

This creates a 3-inch overhang on both the left and right sides, effectively catching the steam that naturally billows outward before it escapes into the room.

Set the Mounting Height by the Spec

Check the manufacturer specifications for your specific insert to determine the mounting height, which usually requires the bottom edge to sit 30 to 36 inches above the grates.

Route Rigid Ducting to the Outside

Plan for smooth, rigid metal ducting that vents completely outside the house to maximize your airflow and keep the kitchen fresh.

Top section of a tapered plaster range hood meeting the kitchen ceiling cleanly. — Smooth rigid pipes minimize airflow resistance and operational noise.

Avoid flexible corrugated pipes entirely, because their ridges trap grease and severely reduce the cubic feet per minute (CFM) your fan can actually move.

Plan the Ducting Path

Finding the shortest, straightest route to the exterior wall or roof is critical for maintaining strong suction and quiet operation.

Locate the joists: Use a stud finder to map out the ceiling joists so your pipe can run parallel between them.
Minimize elbows: Keep turns to an absolute minimum, as every 90-degree bend drastically reduces the effective airflow.
Cut the exterior hole: Drill a pilot hole from the inside, then use a reciprocating saw outside to fit the vent cap.

Frame the Box Around the Cutout

Build the wooden skeleton using standard 2×4 framing lumber, anchoring it directly into the wall studs and ceiling joists to support the heavy plaster finish.

Close-up of a slim oak wood ledge on a plaster range hood holding a salt cellar and oil cruet. — Keep combustible items far above the active heat zones.

Add a Shallow Ledge for Essentials

Incorporate a slim 4-inch oak ledge along the bottom edge of the hood frame to hold your most-used cooking tools.

I added one of these to my own kitchen last year, and having my salt cellar right there while keeping combustible items safely away from direct heat is a total game-changer.

Install Drywall and Corner Bead

Wrap the entire wooden skeleton in half-inch drywall, securing it with coarse-thread screws to create a solid substrate for your final finish.

Finish With a Smooth Clay Plaster

Coat the exterior in a warm-white clay plaster applied in thin layers over the drywall for a seamless, structural look.

Finished warm-white clay-plaster range hood in a bright kitchen with natural light. — Seal porous surfaces to prevent permanent cooking grease stains.

When I plastered my own hood, I learned the hard way that you must seal the plaster thoroughly to protect that beautiful matte surface from inevitable cooking splatters.

Download Your Custom Hood Sizing Sheet

Take the guesswork out of your build by filling in your range width, burner BTUs, and ceiling height on the Custom Range Hood Sizing Sheet.

Wide view of a kitchen featuring a perfectly proportioned custom plaster range hood centered between windows. — Correct proportions make massive architectural features feel entirely intentional.

This instantly gives you the exact hood width, mounting height, minimum CFM, and framed-box dimensions needed to make this massive architectural feature look completely intentional.

Custom Range Hood Design Ideas

Explore these distinctive finishes and shapes to find the perfect look for your kitchen's architecture.

Modern Farmhouse Shiplap: Vertical white shiplap brings subtle texture, while decorative brass strapping adds a polished metallic detail.

White shiplap custom range hood with brass strapping in a rustic kitchen.

Dark Moody Roman Clay: Charcoal roman clay creates a dramatic focal point that pairs beautifully with rich walnut wood trim.

Charcoal roman clay range hood with walnut trim in a moody kitchen.

Tapered Copper Canopy: Aged copper develops a living patina over time, and exposed rivets emphasize an authentic industrial aesthetic.

Aged-copper custom range hood with exposed rivets against a brick wall.

Scalloped French Country: A gentle scalloped detail along the bottom edge softens the large structure for a romantic cottage feel.

Cream painted range hood with a scalloped edge in a cottage kitchen.

Minimalist Fluted Oak: Vertical fluted oak panels conceal the ventilation entirely while adding warm, rhythmic texture to a modern space.