What Is the Garden Arch Calculator?
Our free garden arch calculator gives you the radius, arc length, overall height, and frame material for building a garden arch, archway, or trellis. Enter the width you want to span, how much rise (curve height) you'd like on top, and the height of the legs - and it returns the exact curve geometry plus the linear feet of material to cut, so your arch comes out symmetrical the first time.
How to Use This Calculator
- Enter the arch width (span) - the clear distance between the two legs of the arch.
- Enter the arch rise - how tall the curved top section is above the legs.
- Enter the leg height - the vertical distance from the ground to where the curve begins.
- Set your picket or slat spacing if you want a count for infill pieces.
- Read off the radius, arc length, and overall height, and use the frame-material figure to buy your timber or pipe.
Why Accurate Garden Arch Calculations Matter
A garden arch only looks right when its curve is a true, symmetrical arc - and bending or cutting that curve accurately depends on knowing the radius and arc length before you start. Guessing leads to lopsided arches and wasted material, especially with metal conduit or laminated wood that must be bent to a set radius. Working out the arc length also tells you exactly how much material the curved section needs, which is easy to underestimate because the curve is always longer than the straight span beneath it.