AptoCalc

Most of it sits where your thumbs expect it:

• Angle, Offset, Run, Travel across the top. Type a number and press one to set it; press one with nothing typed to see the answer. Keep pressing Travel for the cut, take-out, gap, fitting angle and, on a cut-down elbow, the inside, centre and outside marks.
• Feet, Inch and / above the numbers: 1 4 Feet 7 Inch 1 / 2.
• 2nd down the left is the shift key; what it gives is printed small above each key. 2nd Offset is the root gap, 2nd Run the cutback, 2nd Travel the roll, 2nd Angle the take-out and cut marks, 2nd Size the elbow.
• Angle takes degrees (4 5 Angle) or a slope as a length (1 Inch Angle is 1″ per foot); press it again for the slope and the % grade.
• Stor and Rcl with 1–9 keep nine numbers. M+ keeps a running total: Rcl Rcl shows it, again the average, again how many.
• Conv does gallons, pounds, flow, pressure, torque, temperature, % grade and drop; 2nd Conv does degrees-minutes-seconds.

What's new here: Cut has its own key, and Visualize (or 2nd Cut) pops your offset up in 3D to turn with a finger. The Tape keeps everything you did. Take-outs are steel butt-weld fittings (ASME B16.9); for anything else type your fitting's take-out and press 2nd Angle. The root gap starts at none unless your site's admin set one: type yours and press 2nd Offset.