A standard countertop microwave is about 21 to 25 inches wide, while over-the-range models are typically 30 inches wide.
Knowing whether a microwave will actually fit your space comes down to one number: the width. But “standard” isn’t a single universal size. For most US kitchens, a standard countertop microwave lands between 21 and 25 inches wide, while over-the-range units are built to the same 30-inch width as standard ranges and cabinets. If the width you have in mind is smaller — say, 16 inches — you’re looking at a compact category, a list of tested options for which you can find in our 16 inch wide microwave roundup.
Standard Microwave Widths by Type
The table below breaks down the typical exterior dimensions for each microwave type. These are the outside measurements, not the cooking space inside.
| Microwave Type | Typical Width | Notes |
|---|---|---|
| Countertop | 21–25 inches | Height 12–15 in; depth 16–20 in with closed door |
| Over-the-range (OTR) | About 30 inches | Compact OTR models may run about 24 inches wide |
| Built-in | Fits 24, 27, or 30-inch openings | Standard cabinet cutout sizes |
| Compact/countertop | Under 21 inches | Includes smaller widths like 16 inches |
Countertop capacity usually runs 0.8 to 2.2 cubic feet, over-the-range models 0.8 to 2.1 cubic feet, and built-ins 1.0 to 2.2 cubic feet. Larger exterior width generally means larger capacity, but that’s not a hard rule.
How to Measure a Microwave Before You Buy
Measure the exterior width across the widest point of the unit, not the interior cavity. The usable cooking space is always smaller than the outside dimensions — a common mistake that leads to a microwave that looks like it fits but blocks a cabinet or sits proud of the counter.
For an over-the-range or built-in replacement, measure the cabinet cutout width and height rather than trusting the old unit’s label, since trim and face frames reduce the actual opening. A unit listed as “standard” for one kitchen can fail to fit another without matching cabinet dimensions.
Also account for door swing and depth. The closed-door depth can differ significantly from the space needed to open the door fully, especially in a corner or under upper cabinets. For over-the-range installations, follow the manufacturer’s installation instructions and verify the unit matches your cabinet and range layout and ventilation requirements — this is not optional. Home Depot’s microwave measuring guide walks through this process in detail.
What “Standard” Actually Means for Your Kitchen
The word “standard” depends on context. For a countertop model, it means roughly 21–25 inches wide — the size most manufacturers build around and most kitchens accommodate. For an over-the-range unit, standard means about 30 inches to line up with common range and cabinet widths. Built-ins are the outlier, sized for specific cabinet openings of 24, 27, or 30 inches.
If you’re replacing an existing over-the-range or built-in microwave, the safest path is matching the exact model class of the old unit. If you’re choosing a countertop model for a specific spot, measure the space first — width, height, and depth — then shop to those numbers. The same advice applies whether you’re eyeing a full-size 30-inch over-the-range unit or a compact model closer to 16 inches wide; the 16-inch category is for tight countertops, and our tested selection of 16 inch wide microwave models shows what actually fits those spaces.
FAQs
How many inches wide is a compact microwave?
A compact countertop microwave typically measures under 21 inches wide, with 16-inch and 18-inch widths common for tight spaces and small kitchens. These smaller units usually offer 0.7 to 0.9 cubic feet of capacity, enough for reheating and small dishes but too small for large platters or family-size casseroles.
Do all over-the-range microwaves fit 30-inch openings?
Most over-the-range microwaves are designed for standard 30-inch-wide openings, but not all. Compact OTR models around 24 inches wide exist for narrower layouts. Always measure your existing cabinet cutout before ordering an OTR replacement, because trim and face frames can reduce the actual opening beyond the listed width.
Is microwave width the same as cooking space?
No. The exterior width of a microwave is always larger than its interior cavity width. A countertop model listed at 24 inches wide might offer only about 18 to 20 inches of usable interior width. Check the cubic-foot capacity and interior dimensions on the spec sheet rather than assuming exterior width equals cooking space.
References & Sources
- Home Depot. “How to Measure a Microwave.” Walks through exterior width, door swing, and cabinet cutout measurement.
- KitchenAid. “What Are Standard Microwave Sizes?” Details typical widths for countertop, over-the-range, and built-in models.
- Maytag. “Microwave Sizes: Your Guide to Standard Dimensions.” Covers capacity ranges tied to microwave types.
