Pick the trim kit's width and measure the opening in your cabinet. You see which makers' trim kits take it by each kit's own sheet, where one is too tight or leaves the edge uncovered, and the microwave each kit is made for.
Your cabinet opening
Your 25½″ × 16¾″ opening takes 1 of the 6 27″ trim kits read: GE JX7227for GE countertop microwaves that call for it · each other kit asks its own cutout — no two of the 6 share one
Quick answer: a built-in microwave’s cabinet opening is set by the trim kit and the microwave together, not by the kit’s 27″ or 30″ width. GE’s kits ask a cutout 25½″ × 16¾″, Samsung’s 30″ the same; Whirlpool’s 23⅛″ × 17⅛″ for a 1.6 cu ft microwave and 25½″ × 17⅛–17 3⁄16″ for a 2.2; Frigidaire’s 24¾–25″ × 16¾–17″; Panasonic’s 25½″ wide (27″ kit) or 28½″ (30″ kit). No two of the six 27″ kits read take the same opening.
How to use the trim kit size finder
- Pick the kit’s width: a 27″ kit finishes a 27″ cabinet, a 30″ kit a 30″ one.
- Measure the opening in the cabinet, not the microwave: its width inside edge to inside edge, its height from the opening’s floor to its top, and, if you can, its depth to the back.
- You get which trim kits read take it by their makers’ own sheets, where one is too tight or leaves the edge uncovered, the microwave each kit is made for, and the opening drawn to scale.
The rule behind the numbers
A trim kit turns a countertop microwave into a built-in one: a frame around the door and ducts that carry the air the microwave needs. Each maker prints the cabinet cutout its kit and microwave go into, often to the sixteenth of an inch. Smaller than the sheet and the microwave does not go in; larger and the frame no longer covers the edge as the maker asks — GE’s 27″ frame overlaps the cutout by 1¼″ at the top, 9⁄16″ on the sides and 1″ at the bottom.
The kit’s width is not what sets the hole. Whirlpool’s 27″ and 30″ kits ask the same cutout — 23⅛″ wide for a 1.6 cu ft microwave, 25½″ for a 2.2 — and only the frame changes; GE’s too. Panasonic’s is the other way round: its 27″ kits ask 25½″ wide and its 30″ kits 28½″. So buy the microwave and its kit first, then cut.
Each kit’s cutout
| Kit | Maker, model | For | Width | Height | Depth |
|---|---|---|---|---|---|
| 27″ | GE JX7227 | GE countertop microwaves that call for it | 25½″ | 16¾″ | 19½″+ (22″ with the outlet inside) |
| 27″ | Whirlpool MTK1627P | 1.6 cu ft countertop | 23⅛″ ± 1⁄16″ | 17⅛″ | 20″+ |
| 27″ | Whirlpool MTK2227P | 2.2 cu ft countertop | 25½″ ± 1⁄16″ | 17⅛–17 3⁄16″ | 22¾″+ |
| 27″ | Panasonic NN-TK722SS | 1.6 cu ft (NN-SE7, SD7, SN7) | 25½″ + 5⁄16″ | 15 5⁄16″ ± 5⁄64″ | 21″+ |
| 27″ | Panasonic NN-TK922SS | 2.2 cu ft (NN-SE9, SD9, SN9) | 25½″ + 5⁄16″ | 17⅜″ ± 5⁄64″ | 21″+ |
| 27″ | Frigidaire GMTK2768AF | Gallery GMBS3068AF | 24¾–25″ | 16¾–17″ | 20″+ |
| 30″ | GE JX7230 | GE countertop microwaves that call for it | 25½″ | 16¾″ | 19½″+ (22″ with the outlet inside) |
| 30″ | Whirlpool MTK1630P | 1.6 cu ft countertop | 23⅛″ ± 1⁄16″ | 17⅛″ | 20″+ |
| 30″ | Whirlpool MTK2230P | 2.2 cu ft countertop | 25½″ ± 1⁄16″ | 17⅛–17 3⁄16″ | 22¾″+ |
| 30″ | Panasonic NN-TK732SS | 1.6 cu ft (NN-SE7, SD7, SN7, ST7) | 28½″ + 5⁄16″ | 15 5⁄16″ ± 5⁄64″ | 21″+ |
| 30″ | Panasonic NN-TK932SS | 2.2 cu ft (NN-SE9, SD9, SN9, ST9) | 28½″ + 5⁄16″ | 17⅜″ ± 5⁄64″ | 21″+ |
| 30″ | Samsung MA-TK8020 | MS19M8020 | 25½″ | 16¾″ | – |
| 30″ | Frigidaire GMTK3068AF | Gallery GMBS3068AF | 24¾–25″ | 16¾–17″ | 20″+ |
“+” after a depth means at least; a dash means no depth in the sheet read. Each row is the maker’s own document: GE’s installation instructions 31-7000345, Whirlpool’s W11667246B (its kits are sold under Whirlpool, KitchenAid, Maytag, JennAir and Amana), each Panasonic kit’s own page, Samsung’s specification sheet and Frigidaire’s instructions A06823528. GE and Samsung print one size with no tolerance; the finder reads it as the size to cut, to the nearest 1⁄32″. Whirlpool’s depths are with a flush outlet in the area its sheet marks; a raised outlet or one elsewhere asks more.
Five worked examples
A 27″ cabinet cut 25½″ × 16¾″, GE’s cutout. It takes GE’s JX7227 only: Frigidaire’s stops at 25″ wide, Whirlpool’s 2.2 cu ft kit asks at least 17⅛″ high.
The same cabinet cut 17⅛″ high, for Whirlpool’s 2.2 cu ft kit. Whirlpool’s MTK2227P goes in; the opening is now ⅜″ taller than GE’s 16¾″.
A 27″ opening 25″ × 16¾″. Frigidaire’s GMTK2768AF takes it; GE’s kit is ½″ too narrow.
A 30″ cabinet cut 25½″ × 16¾″. The one opening two kits share: GE’s JX7230 and Samsung’s MA-TK8020.
A 30″ opening 28½″ × 15 5⁄16″, Panasonic’s. Only Panasonic’s NN-TK732SS takes it; every other 30″ kit read stops at 25 9⁄16″ wide.
Common mistakes
- Cutting the cabinet before buying the kit. The cutout belongs to the kit and the microwave, and they differ by maker: a 25½″ × 16¾″ GE opening is ⅜″ short for Whirlpool’s 2.2 cu ft kit and ½″ wide for Frigidaire’s.
- Thinking the kit’s 27″ or 30″ is the hole. It is the frame — the cabinet it finishes. Whirlpool’s two widths ask one cutout; Panasonic’s ask 3″ apart.
- Buying a kit for another microwave. Frigidaire’s says it is “designed for use only with Electrolux microwave ovens specifying built-in kit”; Panasonic’s lists its own NN- models. Check the kit your microwave’s manual names.
- Forgetting the outlet. GE asks 19½″ of depth with the outlet outside the cabinet and 22″ with it inside; Whirlpool marks where its outlet should sit.
- Blocking the air. GE’s kit “uses air flow from the top, bottom and sides of the trim frame” and asks 1″ clear beyond the frame on all sides.
Size a wall oven or a microwave drawer with the wall oven cutout finder, the microwave over the range with the stove and microwave size finder, and draw the kitchen to scale in the free 2D planner.
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Microwave trim kit questions
What size is a microwave trim kit?
27″ or 30″ wide — the width of the cabinet it finishes. The frames read run 26 13⁄16–30″ wide and 16½–20 5⁄64″ high; the cabinet cutout behind them is smaller and set by the kit and microwave together.
What size cabinet opening does a built-in microwave need?
The one its trim kit’s sheet prints: 25½″ × 16¾″ for GE’s kits and Samsung’s 30″; 23⅛″ × 17⅛″ (1.6 cu ft) or 25½″ × 17⅛–17 3⁄16″ (2.2 cu ft) for Whirlpool’s; 24¾–25″ × 16¾–17″ for Frigidaire’s; 25½″ or 28½″ wide for Panasonic’s.
What is the difference between a 27 inch and a 30 inch microwave trim kit?
The frame, sized to a 27″ or a 30″ cabinet. Whirlpool’s and GE’s two widths ask the same cutout; Panasonic’s 30″ kits ask a cutout 28½″ wide where its 27″ kits ask 25½″.
Is there a universal microwave trim kit?
None of the five makers read sells one: each kit names the microwaves it fits, and their cutouts differ — no two of the six 27″ kits read share an opening.
Can you put a countertop microwave in a cabinet?
Built in, with the trim kit its maker names: the kit carries the air. GE warns that “blocking the air flow can cause the microwave to function improperly”. On an open shelf, follow the space around it that the microwave’s own manual asks.
How deep does a cabinet need to be for a built-in microwave?
19½–22¾″ in the sheets read: GE 19½″ with the outlet outside the cabinet and 22″ inside, Whirlpool 20″ (1.6 cu ft) or 22¾″ (2.2 cu ft) with a flush outlet where it marks, Panasonic 21″, Frigidaire 20″.
How high should a built-in microwave be?
Whirlpool recommends at least 36 1⁄16″ from the floor to the opening’s floor and Panasonic asks at least 36¼″; over a wall oven, GE and Frigidaire ask at least 3″ between the two, Whirlpool 3 15⁄16″ from the oven’s cutout to the microwave’s.