The calculator applies static moment balance to a uniform rigid door supported by an ideal two-hinge pair. It does not rate hinges, screws, jambs or an installation.
Hinge Moment Load Interactive Calculator
Compare door weight, half-width center-of-mass arm, hinge spacing and the ideal horizontal reaction couple required for static equilibrium.
Equation Used
- Uniform rigid door with center of mass at half the entered width.
- Two ideal hinge reaction points separated by the entered vertical spacing.
- Static equilibrium with no acceleration, impact or wind load.
- No hinge-leaf, pin, screw-group, jamb, edge-distance, prying, flexibility, tolerance, fatigue or capacity model.
For a uniform door, the center of mass lies halfway across its width. The calculated force is the magnitude of each opposing horizontal force in the ideal hinge couple, not a per-screw pull-out load or allowable capacity.
Static moment balance
A uniform door's weight acts at its center of mass, halfway from the hinge axis to the latch edge. That gravity moment is balanced in this idealization by equal and opposite horizontal reactions at two hinge points.
The animated swing is only an orientation view. The calculation itself is static and does not vary with the displayed angle.
Use as an equilibrium check only
The result can check the arithmetic of a simplified free-body diagram. It cannot select a hinge, screw, anchor or jamb, and it is not an allowable load.
Center-of-mass lever arm
Door weight is W=mg. For a uniform door of width w, the center-of-mass arm is w/2, not w. Balancing moments gives Fd=W(w/2), hence F=Ww/(2d).
The calculation uses standard gravity 9.80665 m/s². The couple forces have equal magnitude and opposite direction; they also act alongside vertical hinge forces supporting the door’s weight, which this tool does not distribute between hinges.
Transparent example
A 55 kg uniform door is 1,100 mm wide with hinge points 1,200 mm apart. Its weight is about 539.4 N and its center-of-mass arm is 550 mm, giving an ideal horizontal hinge-pair reaction of about 247.2 N.
Each ideal horizontal couple force has this magnitude. It is not the total load on a hinge or a screw-capacity check.
Scope and limitations
Actual fastener and hinge loads depend on center-of-mass offsets, hinge count and load sharing, leaf and frame flexibility, screw layout and embedment, edge distance, material properties, clearances, prying, door acceleration, impact, wind and misuse. Suitable hardware must be assessed from verified manufacturer data and the real installation.
Frequently asked questions
Why is half the width used?
For a uniform door, gravity acts at its geometric center, halfway across the width.
Is the displayed force the pull-out load on each top screw?
No. It is the magnitude of each horizontal force in the ideal hinge couple. Distribution among leaves and fasteners requires the actual geometry and stiffness.
Does opening angle change the result?
For a rigid door swinging about a vertical hinge axis, its center-of-mass distance from that axis stays w/2. The couple magnitude is unchanged in this ideal model; its direction turns with the door.
Why do dimension changes not resize the drawing?
The illustration has fixed proportions. Entered width and hinge spacing change the numerical equilibrium result, not the drawn geometry.
Calculation basis
The weight of a uniform rigid door acts at horizontal distance w/2 from its vertical hinge axis. A horizontal couple with vertical separation d balances that gravity moment: Fd = Ww/2.
The red arrows illustrate the door’s horizontal loads on the frame. The frame’s corresponding forces on the door point in the opposite directions. The green arrow shows gravity acting on the door. The drawing is an orientation illustration, not a complete three-dimensional free-body diagram.
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