Hinge Calculator

Hinge Calculator for cabinet and room doors. Enter the door size and material to get the hinge count and spacing, Blum cup boring and overlay, or a Hager butt hinge size and grade.

Hinge Calculator for Cabinet and Room Doors

The Hinge Calculator works in two modes. For cabinet doors it uses Blum's concealed hinge data to set the hinge count, cup position and overlay. For room doors it follows Hager's butt hinge selection guide to give the size, count and bearing grade.

Door sizes are finished sizes in inches, and weights are in pounds, with a metric option. Cabinet boring numbers stay in millimeters in both modes, because Blum specifies its hinges in millimeters.

How Many Concealed Hinges a Cabinet Door Needs

Blum's US catalog chart sets the count by door height or door weight, whichever needs more hinges. Two hinges cover doors up to 40 in tall and under 15 lb. Three cover 40 to 60 in or 15 to 30 lb, four cover 60 to 80 in or 30 to 45 lb, and five cover 80 to 100 in or 45 to 60 lb.

A 30 by 15 in MDF door at 3/4 in thick weighs about 9.4 lb with its pull, so it takes two hinges at 63% of the two-hinge limit. A 72 by 18 in MDF pantry door weighs about 26.6 lb. Weight alone would call for three hinges, but its height puts it in the four-hinge band, so it gets four.

Width adds its own rule. Blum's hinge counts apply to doors up to 600 mm (23-5/8 in) wide, and Blum's assembly guide adds one hinge for doors up to 650 mm. A 30 by 24 in door at 15 lb gets a third hinge from width alone, even though its weight sits just under the two-hinge limit.

The same Blum guide is stricter on weight than the US chart. It calls two hinges optimal for 4 to 6 kg and three for 6 to 12 kg. A 36 by 20 in MDF door at about 14.9 lb (6.7 kg) with its pull passes the US chart with two hinges, but Blum's European guidance would fit three. Blum also says to count the handle in the door weight.

The Hinge Calculator estimates door weight from typical density for MDF, particleboard, plywood, oak or maple, and pine. Real boards vary, so weigh the door on a bathroom scale if it sits near a band limit, and enter the weight directly.

Hinge Spacing and Top Hinge Pull-Out

Blum's catalog notes that the distance between the top and bottom hinges must be greater than the door width. The tool checks that span and spaces any middle hinges evenly between the two outer ones.

The door hangs off its hinges, so the top hinge is pulled outward while the bottom one is pushed in. Taking moments about the bottom hinge gives the pull on the top one.

$$F=\frac{W\cdot (w/2)}{s}$$

Here $W$ is door weight, $w$ is door width and $s$ is the span between the outer hinges. The default 9.4 lb door, 15 in wide with hinges 22 in apart, pulls 3.2 lb on its top hinge. That load grows with width, which is one reason Blum caps door width rather than only weight.

Overlay, Boring Distance and Mounting Plates

Overlay is how far the closed door covers the cabinet side. Blum gives it as fixed distance plus boring distance minus plate height.

$$OL=X+B-H$$

The fixed distance $X$ is 11 mm for a full overlay CLIP top 110 degree hinge and 1.5 mm for the half overlay version, per the Blum CLIP top BLUMOTION catalog. Boring distance $B$ runs from the door edge to the edge of the 35 mm cup hole, from 3 to 7 mm.

At a 5 mm bore on a 0 mm plate, a full overlay door covers 16 mm (5/8 in) of the side panel. On a 3/4 in panel, that leaves about 3.1 mm of panel edge showing. Two half overlay doors on one shared 3/4 in panel each cover 6.5 mm and leave about 6 mm between them.

The cup center is the boring distance plus the 17.5 mm cup radius, so a 5 mm bore puts it 22.5 mm (7/8 in) from the door edge. The cup is 13 mm deep, with screw or dowel holes 45 mm apart and 9.5 mm behind the cup center.

Plate choice changes the overlay one for one. Blum restricts the 4.5 mm plate to face frame cabinets and the 9 mm plate to frameless panel cabinets, and the tool notes either one when you pick it.

The standard 110 degree hinge handles doors up to 26 mm (1 in) thick. Past that, the tool switches to Blum's 95 degree thick door hinge and stops with a warning above 30 mm. Blum recommends a trial fit for anything thicker than 26 mm.

When the same cabinet holds drawers, the Drawer Box Calculator sizes boxes to Blum and Accuride slide specs. Pull weight belongs in the door weight here, and the Drawer Pull Positioning Calculator marks where those pulls go.

Butt Hinges for Room Doors by Hager's Guide

Room doors follow the Hager commercial hinge catalog. Doors up to 60 in tall get two hinges, plus one for each extra 30 in, so a standard 80 in door takes three. Hager adds an optional extra hinge for doors wider than 37 in to carry the added weight and frame strain.

Hinge height comes from door thickness and width. A 1-3/8 in door takes 3-1/2 in hinges up to 32 in wide and 4 in hinges up to 36 in. A 1-3/4 in door takes 4-1/2 in hinges up to 36 in, 5 in up to 48 in and 6 in beyond that.

Hinge width depends on how far the door must swing past the trim. Hager's formula subtracts the backset from the door thickness, doubles it and adds the clearance needed.

$$W_h=2(T-b)+c$$

The backset $b$ is 1/4 in on most doors and 3/8 in on doors over 2-1/4 in thick. A 1-3/4 in door with 1/2 in of trim projection needs a 3-1/2 in wide leaf. With 2 in of trim projection it needs 5 in, wider than the 4-1/2 in hinge is tall, which Hager calls a wide throw hinge. A hollow metal frame insets the door about 1/8 in, and the tool adds that to the clearance.

Weight and use frequency set the bearing grade. Hager rates 5 in hinges at 100 lb for low use with plain bearings and 175 lb for medium or high use with ball bearings, for doors up to 36 in wide.

A 42 in wide, 1-3/4 in solid-core door weighs about 86 lb by the tool's estimate. It gets four 5 in hinges, three for its height plus one for width, and plain bearings carry it. Hager's ratings assume doors up to 36 in wide, so the tool flags the extra width. The same door in solid oak comes to about 151 lb, past the plain bearing rating, so the tool steps it up to ball bearing hinges.

Each mortise is cut as deep as one hinge leaf is thick, so the door closes flush. The tool lists that depth along with a screw count for the hinge size.

Door Hinge Calculator Answers

How many hinges does an exterior door need?

A standard 80 in entry door needs three hinges under Hager's height rule, no matter how light it is. If the door is wider than 37 in, Hager suggests a fourth hinge for the extra weight and frame strain.

Most exterior doors are 1-3/4 in thick, so a 36 in door takes 4-1/2 in hinges and a 42 in door takes 5 in hinges. Entry doors open often, so set the use to medium, which moves the tool to ball bearing hinges.

Where do door hinges go on the door?

Commercial hardware guides place the top hinge 5 in below the head jamb rabbet and the bottom hinge 10 in above the finished floor, with any middle hinge centered between them. Those figures are measured from the frame and floor, not the door.

The Hinge Calculator measures from the door's own edges, with defaults of 7 in from the top and 11 in from the bottom. To match the 5 and 10 in layout instead, subtract the gap at the head and the gap under the door. With a 1/8 in head gap and 3/4 in under the door, that comes to about 4-7/8 in and 9-1/4 in.

How do I weigh a cabinet door for hinge selection?

Stand on a bathroom scale holding the door, then subtract your own weight. Include the pull or handle, since Blum counts hardware in the door weight and a long bar pull can push a door into the next band.

If the door is not built yet, the tool's density estimate is close enough unless the result lands near a band limit. The tool marks the weight card amber above 90% of the band limit, and that is the point to weigh before you drill.