Garage Door Spring Size Calculator

Understanding Garage Door Spring Sizing

Garage door springs counterbalance the weight of the door, making it possible to open manually or with a small electric opener. Without properly sized springs, the door would be too heavy to lift. There are two spring systems: torsion springs (mounted above the door on a shaft) and extension springs (mounted on each side along the horizontal tracks). Torsion springs are preferred for their smoother operation, longer life, and safer failure mode.

Door Weight by Size and Material:

Torsion Spring Specifications:

Torsion springs are defined by three measurements: wire diameter, inside coil diameter, and length. The spring must store enough energy (measured in inch-pounds) to lift the door through its full travel, which is simply the weight it lifts multiplied by how far it lifts it:

Spring Energy (in-lb) = Door Weight (lb) x Door Height (inches)

A 7 foot door travels 84 inches, so a 200 pound door needs a spring holding about 16,800 inch-pounds. Use inches for the height, not feet: mixing the units here is the single most common arithmetic slip on this page’s subject, and it lands you a factor of twelve out.

Common torsion spring wire diameters range from 0.207 inches (5.3 mm) for light single-car doors to 0.295 inches (7.5 mm) for heavy double-car doors. The inside coil diameter is typically 1.75 inches (44 mm) or 2 inches (51 mm) for residential applications.

Spring Cycle Life:

Springs are rated by cycle life, where one cycle equals one full open-and-close operation. Standard springs are rated for 10,000 cycles, which lasts approximately 7 to 10 years with average use (3 to 4 cycles per day). High-cycle springs rated for 25,000 to 50,000 cycles cost more initially but last 2 to 5 times longer, making them a better value for busy households.

Opener Motor Size:

The garage door opener motor must be powerful enough to lift and lower the door smoothly. Since the springs do most of the lifting, the opener mainly needs to overcome friction and provide controlled movement.

• 1/3 HP (0.25 kW): Single-car uninsulated steel or aluminum doors up to 150 lb (68 kg)
• 1/2 HP (0.37 kW): Standard single-car insulated doors up to 200 lb (91 kg)
• 3/4 HP (0.56 kW): Double-car doors and heavier single-car doors up to 300 lb (136 kg)
• 1 HP (0.75 kW): Heavy custom wood doors and oversized doors up to 400 lb (181 kg)
• 1-1/4 HP (0.93 kW): Commercial and extra-heavy doors over 400 lb (181 kg)

Safety Warning:

Garage door springs store tremendous energy and can cause serious injury or death if they break or are improperly handled. Torsion spring replacement should be performed by a trained technician with proper tools. A spring for a 200-pound, 7-foot door holds about 16,800 inch-pounds, and a winding bar that slips releases all of it in a fraction of a second. Never attempt to adjust or replace torsion springs without professional training and the correct winding bars.