SM Offset: Duct Calculator

SM Offset is a field calculator for sheet metal workers, HVAC fabricators and pipefitters, built by a working sheet metal tradesman. Every calculator is free, it works with no signal, and answers come out in real tape-measure fractions.

ROUND
• Two-elbow offset: cut joint, travel and multiplier for a flat offset
• Rolling offset: rise and roll combined into one true offset, with the cut length to match

RECTANGULAR
• Radius elbows: two radius elbows plus a straight joint, with cut joint, travel and multiplier
• Mitered offset: square-throat elbows, with cheek length and miter setback
• Offset in a length: drop in the run you have, and the app works out the angle

TOOLS
• Duct resizer: something in the way? Shrink a side, keep the airflow
• Equivalent duct: round to rectangular and back (ASHRAE equal-friction and equal-area)
• Fraction ⇄ decimal, right triangle (any two values), arc length

SEND IT TO THE CREW
• Share any offset result as a text, with every size, angle and cut length

WHY TRADES TRUST IT
• Every offset is exact trig, cross-checked two independent ways
• A live drawing of the fitting as you type
• Fractions to 1/16" (or 1/32"), decimals, or metric
• Your shop's connection allowance, set once
• Recent calculations saved automatically
• Fast, dark, glove-friendly

Whether you're laying out ductwork in the shop or solving an offset on the roof, SM Offset gives you numbers you can cut to.