Garage Door Torsion Spring Calculator

Find the lifting capacity, turns and life cycles of a garage door torsion spring from its wire size, inner diameter and length.

Units Inches / lbs mm / kg
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How to use this garage door spring calculator

This free calculator tells you how much weight a garage door torsion spring can lift, how many turns it needs and how long it should last. Use it to check the springs on your door before you order replacements, or to compare two spring sizes. No sign-up, and it works in inches or millimetres.

  1. Wire size: measure 10 coils and divide by 10. See the wire size guide.
  2. Inside diameter: usually 1 3/4" or 2" on home garage doors. See the inside diameter guide.
  3. Length: measure the wound coils only, not the cones. See the spring length guide.
  4. Door height, track radius and drum: these set the number of turns. See how to measure door height and find your track radius.
  5. Press Calculate.

Example

A spring with .225 wire, a 2" inside diameter and 25" of coils, on a 7 ft door with 15" radius track and standard 4" drums, lifts 111.9 lb at 7.94 turns and should last about 13,000 cycles. Two of them balance a door of about 224 lb.

What the results mean

  • Lifting capacity is the door weight one spring balances. Add the springs together for the whole door: the total should be close to what the door weighs.
  • Turns is how many full turns the spring is wound with the door closed.
  • Cycle life is an estimate of how many open-and-close cycles the spring lasts before it breaks. 10,000 cycles is the usual standard.

Don't know what your springs should be? Start from the door instead: the spring size calculator by door weight lists springs that fit, and the buying guide explains what to measure.

Frequently Asked Questions

How do I find my spring's wire size?

Measure the length of 10 coils with a tape measure and divide by 10. For example, if 10 coils measure 2.25 inches, the wire size is 0.225. Our wire size guide shows the process step by step.

What drum size does the calculator assume?

The standard 4 inch residential cable drum. If your door uses a 5.25 inch drum, common on taller doors, select it in the Drum dropdown and the results adjust automatically.

What does the life cycles number mean?

One cycle is one full open and close of the door. The number is an engineering estimate of the spring's fatigue life at the calculated stress. Rust, missing lubrication and poor balance shorten it.

Why is lifting capacity shown per spring?

Most doors use a pair of springs that share the load. If your door has two springs, together they lift twice the shown capacity, so each spring should be sized for half the door weight.

How many turns does a 7 ft garage door need?

On standard 4 inch drums, a 7 ft door needs about 7.9 turns with 15 inch radius track, 7.6 turns with 12 inch radius track and 7.2 turns with low headroom track. An 8 ft door needs about 8.8, 8.5 and 8.1 turns. The calculator works out the exact number for any door height.

How do I check that a spring is right for my door?

Enter the spring's size with your door height and add up the lifting capacity of all the springs on the door. The total should be close to the door's weight. Well under, and the door feels heavy and drops; well over, and it drifts up on its own.

What if I do not know my door's weight?

Use our door weight calculator to estimate it from the size and material, then use the spring size calculator by door weight to get matched spring options.

Is this garage door spring calculator free?

Yes. It is free with no sign-up, and it works in inches and pounds or in millimetres and kilograms.