Measuring a cooktop means capturing two sets of numbers: the countertop cutout (the hole your cooktop sits in) and the clearances around it. Getting these right is the difference between a cooktop that drops in cleanly and one that doesn’t fit. You’ll need a tape measure and about ten minutes.
Cutout vs. Overall Dimensions
Every cooktop has two size specs that matter. The overall dimensions describe the outer edges of the unit, including the lip or flange that rests on your countertop. The cutout dimensions describe the hole in the countertop the cooktop drops into. When you’re shopping for a replacement, the cutout is the measurement that determines whether a new unit will fit. The overall dimensions tell you how much counter surface the cooktop will cover.
Most cooktops come in two standard widths: 30 inches and 36 inches. A 30-inch model typically has four burners and works well in smaller kitchens. A 36-inch model usually offers five or six burners and suits larger kitchens or anyone who regularly cooks multiple dishes at once. The actual cutout for each size is smaller than the name suggests, so always check the manufacturer’s spec sheet rather than assuming.
How to Measure the Cutout
If you’re replacing an existing cooktop, remove the old unit first so you can measure the opening directly. Here’s how to get accurate numbers:
Width: Run your tape measure from the left edge of the cutout to the right edge. Take this measurement twice: once near the front of the opening and once near the back. Countertop cutouts aren’t always perfectly square, especially in older homes. If the two numbers differ, use the smaller one.
Depth (front to back): Measure from the front edge of the cutout to the back edge. Again, take two readings: one near the right side and one near the left. Use the smaller number if they don’t match.
Corner radius: If your cutout has rounded corners, note the radius. Some cooktops require sharper or more rounded corners than others, and a mismatch can leave gaps or prevent the unit from seating properly.
For a brand-new installation where no cutout exists yet, you’ll work from the cooktop manufacturer’s cutout template, which comes with the unit or is available in the installation guide online. Mark the template on your countertop and have the cutout made to those exact specs.
Measuring the Counter Edge Clearance
The cutout can’t sit right at the edge of your countertop. You need enough material between the cutout and the front edge of the counter for structural support and for the cooktop’s flange to rest on. One installation guide specifies a minimum of 2.5 inches from the edge of the cutout to the front edge of the countertop. Check your specific model’s requirements, but that figure is a reliable baseline.
Side clearances matter too. Measure the distance from each side of the cutout to the nearest wall or tall cabinet. Most manufacturers require a few inches of clearance on each side to prevent heat damage to adjacent surfaces. This number varies by model, so pull the spec sheet before you finalize placement.
Vertical Clearance Above the Cooktop
Building codes require at least 30 inches of vertical clearance between the cooking surface and any combustible material above it, including wood cabinets. That distance drops to 24 inches if you have a metal range hood installed above the cooktop or if the underside of the cabinet is protected with insulating board covered by sheet metal.
Measure straight up from where the cooktop surface will sit to the bottom of your overhead cabinets or any other material above. If you’re installing a range hood, the most common size is 30 inches wide to match standard cooktops. Position it so you meet that 24- or 30-inch minimum depending on your setup.
Space Below the Countertop
Cooktops need room underneath for their components and for airflow. How much room depends on the type of cooktop and what’s below it.
If you’re installing an oven beneath the cooktop, you’ll need at least 1 inch of clearance between the bottom of the countertop and the top of the oven. Measure the depth of the space inside your base cabinet from the underside of the counter down to whatever’s below, whether that’s a shelf, an oven, or the cabinet floor.
Electric and induction cooktops need space for their wiring. Plan for about 2 inches of clearance below the cable opening so the electrical connection and junction box can be installed comfortably. The junction box is typically mounted on the wall behind the cooktop, and the cable needs enough slack to allow the unit to be pulled forward for servicing later.
Extra Measurements for Downdraft Models
Downdraft cooktops have a built-in ventilation system that pulls smoke and steam downward instead of relying on an overhead hood. This means there’s a blower motor housed beneath the cooking surface that takes up significantly more cabinet space than a standard cooktop.
On one popular downdraft model from JennAir, the blower motor and plenum assembly is about 14.5 inches wide, and the total height from the blower to the underside of the cooktop is over 18 inches. You need a minimum of 2 inches between the blower motor and the cabinet walls for cooling, and 6 inches is recommended if you want reasonable access for servicing. Measure the interior of your base cabinet carefully: height, width, and depth. Compare those numbers against the manufacturer’s dimension guide before committing to a downdraft unit.
Gas vs. Electric: What Changes
For electric or induction cooktops, your main concern below the counter is routing the armored cable to a junction box. The cable typically passes through a 4-by-4-inch opening cut in the base cabinet, positioned about 2 inches from the side panel. Make sure you know where your electrical supply enters the cabinet so you can plan the cable path.
Gas cooktops add a different variable: the gas supply line. You’ll need to confirm the location of the gas shutoff valve and ensure there’s enough room behind or below the cooktop for the flexible connector to reach without kinking. Gas line regulators must vent at least 3 feet from any ignition source per national fuel gas code. While the gas company or installer handles the connection, knowing where your supply line enters the cabinet helps you confirm the cooktop will work in the space.
Tips for Accurate Measurements
- Measure twice at different points. Cutouts shift over time, especially in natural stone or older laminate. Taking two readings for each dimension and using the smaller number prevents ordering a cooktop that’s a fraction too wide.
- Use a rigid tape measure. A cloth sewing tape can flex and introduce error. A standard retractable steel tape measure gives you reliable readings.
- Record depth below the counter. Many people measure only the cutout and forget the vertical space inside the cabinet. A cooktop that fits the hole but bottoms out against a shelf or drawer rail won’t install properly.
- Check the countertop thickness. Some cooktop mounting clips are designed for countertops of a specific thickness, typically 3/4 inch to 1.25 inches. Measure the thickness at the edge of the cutout to confirm compatibility.
- Write everything down. Bring your measurements to the store or have them on hand when shopping online. The numbers you need to match are the cutout width, cutout depth, minimum countertop edge distance, and below-counter depth.