Reference · Formula

Spring torque formula

Torque for a torsion spring assembly is expressed in inch-pounds per turn (IPPT). The desk computes the required IPPT for the whole door, then splits it across two springs.

Required IPPT = door weight (lb) × door height (ft) × 1.6π ÷ available turns

1.6π is about 5.0265. The result is rounded to the nearest 0.1 IPPT. Each spring must carry half of the rounded value, so the chosen wire's rated IPPT has to be at least that half.

Example

150 × 7 × 1.6π ÷ 7.5 = 703.7 IPPT · half = 351.85 · smallest wire covering it: .281 in (372 IPPT)

Inputs that stop the calculation

Weight, height, and turns must each be greater than zero. When half the required torque exceeds 372 IPPT, the largest catalog wire, no two-spring residential assembly is scheduled.

Run the formula on your measurements

Torsion springs store dangerous energy. These figures are planning guidance based on entered measurements. A trained garage-door professional must verify measurements, spring compatibility, winding direction, hardware limits, and safe winding procedures.