Cabinet Knob Sizing Guide: Diameter, Projection and Fixing Explained

Cabinet knobs look simple, but a knob that is a few millimetres too small, too tall or fixed with the wrong bolt is one of the most common hardware mistakes in a kitchen or vanity. Because a knob is held by a single fixing point, the details that matter are different to those for a pull handle: diameter, projection, base size and bolt length. This guide covers each one, so you can specify cabinet knobs with confidence before joinery is drilled.

Start With Diameter

Diameter is the width of the knob head and the number that most affects how it looks and feels. As a general guide:

• 25mm to 30mm suits small drawers, bedside tables, vanity drawers and upper cupboard doors where the knob should stay discreet.
• 32mm to 38mm is the most versatile range for kitchen base doors and standard drawers, comfortable to grip without dominating the door face.
• 40mm and above suits wide pantry doors, deep pot drawers and statement joinery, where a small knob would look undersized.

A useful rule is to keep the knob diameter under roughly one-tenth of the width of the door or drawer front it sits on. A 35mm knob on a 600mm door looks balanced; the same knob on a 300mm-wide door starts to feel heavy.

Check the Projection

Projection is how far the knob stands out from the cabinet face. Most cabinet knobs project between 25mm and 35mm. This matters for two practical reasons. First, in a tight galley kitchen or a narrow hallway cupboard, a deeper knob can catch hips, sleeves and bags. Second, when cabinets sit close to appliances or return panels, a knob that projects too far can strike the neighbouring surface as the door opens. As a rule of thumb, keep at least 5mm of clearance between the knob and anything it swings past.

Base Size and Backplate Options

The base (or rose) is the small disc where the knob meets the door. A wider base spreads load across the door face and gives a more substantial look, while a slim base keeps the knob light and minimal. If you are replacing existing knobs, check that the new base covers any old screw marks or paint shadows; a base at least 5mm wider than the old one usually hides them.

Bolt Length and Panel Thickness

A knob is fixed from behind with a machine bolt, so the bolt must suit the thickness of the door or drawer front. Most cabinet doors are 16mm to 19mm thick, while some drawer fronts and solid timber panels run 25mm or more. Measure the actual panel, and add the knob's own fixing depth to work out the bolt length you need. A bolt that is too short will not engage properly and can loosen over time; one that is too long will bottom out before the knob sits tight. Where a panel is unusually thick, confirm longer bolts are available at the time of ordering rather than cutting down a standard one on site.

How Many Knobs, and Where to Place Them

On a standard drawer, one knob centred horizontally is the usual approach. Drawers wider than about 600mm are better served by two knobs, placed roughly one-quarter of the way in from each side, so the drawer does not twist when pulled from one point. On cupboard doors, place the knob on the side opposite the hinge, typically 50mm to 75mm in from the edge and about 50mm down from the top of a base door or up from the bottom of an upper door. For the full placement logic, see our guide to cabinet hardware placement.

Using Knobs Alongside Pulls

Many well-resolved kitchens use knobs on doors and pulls on drawers. The pairing works because a knob suits a light, quick opening action while a pull gives a secure full-hand grip on a heavy drawer stacked with pots. Keep the two in the same finish, and keep the visual weight similar: a 35mm knob pairs comfortably with a pull of around 128mm to 160mm centres. Our guide to matching door handles and cabinet hardware goes deeper on coordinating across a whole home.

Finish and Detail Options

Solid brass cabinet knobs are made to order across the full finish range: Brushed Brass, Antique Brass, Aged Brass, Black Brass, Nickel, Polished Nickel and Aged Nickel. For added texture, the Cavallo range adds leather detailing, Pietra introduces marble, and Legno brings in timber, each giving a knob a distinct tactile quality. Choose one finish per room, and avoid placing Antique Brass and Aged Brass side by side, as the difference reads as a mismatch rather than a choice.

A Quick Cabinet Knob Checklist

• Measure door and drawer widths, then pick a diameter no more than about one-tenth of the smallest front.
• Check projection against nearby walls, appliances and narrow walkways.
• Measure panel thickness and confirm the bolt length before ordering.
• Decide where drawers need one knob and where they need two.
• Choose a single finish family for the room and confirm it against a sample.
• Allow for made-to-order lead time, and order all cabinet hardware for a project together so finishes match.

Solid brass cabinet knobs start from around $35 each, so a full kitchen is a meaningful line in the budget. Getting diameter, projection and bolt length right on paper first means every knob sits square, feels right in the hand and stays tight for years.