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How to size hinges

clock 4 minutes | 09 Oct 2019

Heavy duty hinges types laid out ready for engineer to use

From concealed door hinges to stainless steel lift off hinges, your choices are vast. And no matter what your application, be it a data cabinet or outdoor cable enclosure, your hinges have their work cut out for them. You need to think about:

  • The door size, both height and width
  • The suspended weight
  • The construction of the door, including the material
  • The intended use and/or traffic expected through the door

Sizing the hinge properly is crucial. For instance, undersized concealed hinges can cause premature failure of the door and create safety issues.

First, let's look at the anatomy of a hinge, which all styles share to a degree. This will be important to understand when calculating the size of the hinge needed.

Hinge Vocabulary

  • Leaf – The flat, rectangular portion of the hinge that attaches to the door or door jamb is the leaf. A standard hinge consists of two leaves.
  • Knuckle/Barrel – These are the circular rolled, hollow "barrels" through which the hinge pin is inserted. They allow the hinge to bend, just like the knuckle joints on your fingers. The term knuckle and barrel are often used interchangeably. The knuckles on one leaf are offset from those on the other to allow them to mesh. The measurement from the top barrel to the bottom barrel – measured parallel to the pin – is called the barrel length.
  • Pin – The rod that's inserted into the knuckles to join the hinge leaves.
  • Leaf height – The overall length of the leaf, measured parallel to the pin is the leaf height.
  • Leaf width – This is the dimension measured from the centre of the pin to the outer edge of the leaf, opposite the knuckle or barrel. Don't confuse this dimension with the following dimension.
  • Hinge/open leaf width – This is the overall width of the opened hinge, measured perpendicular to the hinge pin. This will be an important dimension to understand when calculating, ordering, or specifying a hinge or hinge set.
  • Hinge backset – While not part of the hinge itself, it's important to know this dimension for your hinge size calculations. This is the distance the edge of the hinge is set back from the door face.
  • Clearance – Clearance is best described as the gap between the door and the frame or jamb with the door in the fully open position. This is an important measurement for your calculation as it's used to keep the door from contacting trim pieces on the outer face of the frame.

Now that we know what these terms are, let's see how they're used in choosing the correct hinge size for your application.

Screw mounted hinge being installed on an HVAC unit

Hinge Size Calculation

As noted, the two hinge dimensions we're concerned with are the leaf or hinge height and the overall hinge width (measured with the hinge in the fully opened position).

The hinge height required is determined by the door thickness and the door width. The width of the door is important, because it affects the weight of the door. A wider door will need more load-bearing support for stability.

For example, if the door is 1-3/8 inches thick and the width is no more than 32 inches, the hinge height is 3-1/2 inches. However, if the door is between 32 inches and 36 inches, the leaf height of the hinges must be increased to 4 inches to handle the increased weight.

Here's a simple chart to help determine the leaf height dimension:

Door thickness
Door width
Approximate hinge height
1-3/8" Up to 32" 3-1/2"
1-3/8" 32"-36" 4"
1-3/4" Up to 36" 4-1/2"
1-3/4" 36"-48" 5"
1-3/4" Over 48" 6"
2", 2-2/4", 2-1/2" Up to 42" 5" (commercial duty)
2", 2-1/4", 2-1/2" Over 43" 6" (commercial duty)

The next step is to determine the overall hinge width, keeping in mind that this is measured with the hinge fully open, also called the full leaf span.

The minimum width can be determined by a simple calculation using three dimensions:

  • Door thickness
  • Backset
  • Clearance required

To determine backset, here is a general rule of thumb: For door thickness from 1-3/8 inches up to 2-1/4 inches, the standard backset is ¼ inch. For 2-1/2 inches door thicknesses, the standard backset is 3/8 inches.

Determine how much clearance you'll need to keep the door from contacting the casing or trim.

Then, use this formula to calculate the hinge width: (Door thickness – backset) x 2 + required clearance = overall hinge width

If your calculation result isn't a standard hinge size, go to the next size up.

You can use this next chart to help determine the hinge width as well. Just be sure to check it with your individual application for accuracy.

Door thickness
Standard Backset
Max Clearance Provided
Approximate Hinge Width
1-3/8" 1/4" 1-1/4"
1-3/4"
3-1/2"
1-3/4" 1/4" 1"
1-1/2"
2"
3"
4"
4-1/2"
5"
6"
2" 1/4" 1"
1-1/2"
2-1/2"
4-1/2"
5"
6"
2-1/4" 1/4" 1"
2"
5"
6"
2-1/2" 3/8" 3/4"
1-3/4"
5"
6"
Concealed hinge being fitted to a door

Final thoughts

These calculations and charts should help you in choosing the correct size door hinge for your application. Here are a few more tips.

The height of the door is used to determine how many butt hinges you need. In general, you'll want to use one hinge for every 30 inches of door height. For example:

  • Use two hinges for doors up to 60 inches tall
  • Use three hinges if the door is between 60 and 90 inches tall
  • For doors between 90 inches and 120 inches, use four hinges

If your door is between 37 inches and 120 inches wide, installing an extra hinge will supply added strength to support the additional weight and tension being applied to the frame.

Finally, the material used for the hinge can make a difference in its longevity and strength. For large doors, heavy duty hinges types support the weight and can be painted to match. If it works with your application, think about heavy duty steel hinges.

When corrosion and chemicals are problematic, consider using stainless steel hinges. What about aesthetics? Brass vs steel piano hinge, for instance? Brass hinges enhance the overall appearance. However, keep in mind that brass doesn't have the strength of steel or stainless steel. Never sacrifice safety for appearance.

If you need help sizing your hinge, Essentra Components is happy to help. We offer a vast range of hinges, and we can help you decide which one is perfect for your application:

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