How Many Hinges Does a Commercial Door Need?
, by United Doors and Locks, 3 min reading time
Hinge count comes from door height, and hinge size and weight come from door width and mass. The standard schedule, plus when to go heavier.
Hinge count is one of the few parts of a hardware schedule with a genuinely simple answer. It comes from door height. Hinge size and weight come from door width and mass, and those are where most mistakes actually happen.
The standard schedule
For doors 1-3/8 to 1-3/4 inches thick, the accepted industry schedule is:
| Door height | Hinges |
|---|---|
| Up to 60 inches | 2 |
| 60 to 90 inches | 3 |
| 90 to 120 inches | 4 |
| Each additional 30 inches | Add 1 |
A standard commercial door is 7 feet, or 84 inches, so it takes three hinges. An 8-foot door takes four. That covers the great majority of openings you will ever schedule.
Note that the count is not about carrying weight in the way people assume. Three hinges on an 84-inch door are not there because two could not hold it; they are there to keep the door from twisting and to stop the leaf warping over years of use. The middle hinge does very little work when the door is new and a great deal once the door has settled.
Hinge size comes from door width and thickness
Height gives you the count. Width and thickness give you the size:
| Door thickness | Door width | Hinge height |
|---|---|---|
| 1-3/8 in | Up to 36 in | 3-1/2 in |
| 1-3/4 in | Up to 36 in | 4-1/2 in |
| 1-3/4 in | 36 to 48 in | 5 in |
| 2 in and over | Up to 42 in | 5 in heavy weight |
The 4-1/2 by 4-1/2 inch hinge is the commercial default because the standard commercial door is 1-3/4 inches thick and under 36 inches wide. That is why the H4545 Series ball bearing hinge and its plain bearing counterpart cover so much of the market.
When to specify heavy weight
Standard weight hinges are sufficient for doors up to roughly 200 pounds in normal-frequency service. Move to heavy weight when any of the following is true:
- The door exceeds about 200 pounds — lead-lined, acoustic, or heavy-gauge steel doors reach this easily.
- The door is wider than 36 inches, which increases the leverage on every hinge.
- The opening is high frequency: a school corridor, a hospital ward, a busy retail entrance.
A heavy weight hinge such as the Ives 5BB1HW series uses thicker leaves and a larger pin, and it is a considerably cheaper decision than replacing a sagging door later.
Adding a fourth hinge to a 7-foot door
This comes up regularly and it is usually the wrong fix. A standard-height door that sags does not need a fourth hinge; it needs the correct hinge weight, correctly installed screws, and a frame that has not been pulled out of square. Adding hinges to compensate for undersized ones distributes the same inadequate strength across more points.
The exception is a very wide or very heavy door at standard height, where a fourth hinge does meaningfully reduce the load per point. If you are considering it, specify heavy weight hinges first and add the fourth only if the door is both over 200 pounds and over 36 inches wide.
Continuous hinges as an alternative
On the hardest-worked openings, the question stops being how many hinges and becomes whether to use butt hinges at all. A continuous geared hinge such as the FMHD full mortise continuous gear hinge runs the full height of the door and distributes load along the entire edge instead of three points. It costs more up front and it eliminates the sag-and-replace cycle on doors that would otherwise need attention every few years.
Fire-rated doors
On a rated assembly, the hinges are part of the listing. Use hinges of the type and material the listing calls for, keep the count at or above the schedule, and use steel — not aluminium — ball bearing hinges. Substituting a hinge on a fire door can void the label even when the substitute is mechanically stronger.
Send us the door sizes, weights, and frequency and we will schedule the hinges against them.