Pick two-legs or leg-plus-hypotenuse mode and enter the sides — the missing side, both angles, and the 3-4-5 check solve live.
Any unit — ft, in, m. Output matches.
Hypotenuse
5
UNITS
Bill of materials+0% waste
Hypotenuse
same unit as inputs
Net √(3² + 4²) · Waste —
Angles
acute angles, sum to 90°
Net atan2 based · Waste —
3-4-5 square check
corners are square
Net within 1% of ratio · Waste —
Cost projection
Saved on this device · No account · No cloud
Hypotenuse
5
Two legs: hypotenuse = √(a² + b²) — 3 and 4 give exactly 5.
Pick two-legs or leg-plus-hypotenuse mode and enter the sides — the missing side, both angles, and the 3-4-5 check solve live.
Leg + hypotenuse: missing leg = √(c² − a²); the hypotenuse must be the longest side.
Acute angles come from atan2 — a 3-4-5 triangle gives 36.87° and 53.13°.
The 3-4-5 check confirms square corners: if sides match the ratio within 1%, your layout is square.
c = √(a² + b²)
A triangle with legs of 3 and 4 units has a diagonal of exactly 5 units, because 3 squared plus 4 squared equals 5 squared. The ratio scales to any size, so 6-8-10 and 9-12-15 work the same way.
Measure 3 ft along one wall and 4 ft along the other, then measure the diagonal: it must be exactly 5 ft. This tool runs the 3-4-5 check for any size and confirms the layout is square when the ratio matches within 1%.
36.87 degrees opposite the 3 side and 53.13 degrees opposite the 4 side; the two acute angles always sum to 90 degrees. The tool computes both angles from atan2 for any sides you enter.
Enter two legs to get the hypotenuse from c = sqrt(a squared + b squared), or enter a leg plus the hypotenuse to get the missing leg from sqrt(c squared - a squared). The hypotenuse must be the longest side.
Yes: feet, inches, or meters. All outputs, including the hypotenuse, angles, and the 3-4-5 square check, use whatever unit you enter.
Keep estimating
More field converters & master proposal calculators for this job.