Sheet Metal Calculators & Reference Charts
Four calculators our shop floor actually uses: bend deduction and flat pattern length, minimum bend radius with hole and slot clearances, material weight, and gauge to decimal thickness. Every number runs live in your browser. Nothing to download, no email required, no signup.
These are the same rules of thumb we apply when we review a customer print before it hits the laser. They will get you close on a flat pattern, a material callout or a shipping weight. They will not replace a test bend on your exact tooling, and we say so where it matters. Bookmark this page — it works on your phone at a workbench as well as it does on a workstation.
Why These Four Numbers Matter
Most sheet metal parts that come back wrong come back wrong for one of four reasons. The flat pattern was developed with the wrong bend deduction, so every formed dimension is off. The inside radius was drawn tighter than the material can take, so the outside of the bend cracked. A hole was placed too close to a bend line, so forming pulled it out of round. Or gauge was called out instead of decimal thickness, and the shop pulled 16 gauge aluminum when the print meant 16 gauge steel — nine thousandths of an inch apart.
None of those are exotic failures. They are arithmetic. The calculators below handle the arithmetic so you can spend your time on the design. If you want the reasoning behind the numbers rather than just the numbers, our sheet metal design for manufacturability guide walks through bend relief, feature spacing, hardware insertion and how to dimension a drawing so a fabricator reads it the way you meant it. For cutting capacity and what thicknesses we can process on each machine, see our laser cutting thickness and capacity page.
Bend Deduction & Flat Pattern Length
When sheet metal bends, the outside stretches and the inside compresses. The neutral axis — the line that does neither — shifts toward the inside of the bend. That is why a flat blank is always shorter than the sum of the finished outside dimensions. Bend deduction is how much shorter. Enter your thickness, inside radius, angle and K-factor and this returns bend allowance, outside setback, bend deduction, and the developed flat length if you add your two outside legs.
Outside setback = tan(angle ÷ 2) × (R + T)
Bend deduction = (2 × OSSB) − BA
Flat length = leg A + leg B − BD
Minimum Bend Radius & Feature Clearance
Pick a material and enter a thickness. This returns the minimum inside bend radius we would run without expecting cracking, the shortest flange standard tooling can hold, how far a hole or slot has to sit from the bend line to survive forming, and the bend relief we would cut at the ends of a partial bend. These are starting points for air bending. Temper and grain direction move them. Bending across the grain tolerates a tighter radius than bending with it, which is why 6061-T6 in the wrong orientation cracks at a radius 5052 shrugs off.
Sheet Metal Weight Calculator
Weight drives freight cost, drives whether a panel is a one-person install or a two-person install, and drives the structural math on anything that hangs. Enter a flat blank size and quantity and this returns weight each and weight per lot in both pounds and kilograms, for twelve alloys from 5052 aluminum through 316L stainless and titanium. It calculates the solid blank, so subtract your large cutouts for a closer number.
Gauge To Decimal Thickness Converter
Gauge is not a unit of measure. It is a leftover from wire drawing, and every material family kept its own table, which is why 16 gauge steel is 0.0598 inch and 16 gauge aluminum is 0.0508 inch. Ten thousandths apart on the same number. Pick a material family and a gauge to get decimal inches and millimeters. If you want the full printable chart across every gauge and material at once, it lives on our cutting capacity and thickness page.
K-Factor, Density & Radius By Material
Default values the calculators above use. K-factor is where the neutral axis sits as a fraction of thickness — softer, more ductile material pushes it toward the middle, harder material pulls it toward the inside face. Minimum radius is expressed as a multiple of material thickness. Verify with a test bend on your tooling before you commit a production run.
6061-T6 — K 0.33, 0.0975 lb/in³, min radius 3×T
3003 — K 0.33, 0.0990 lb/in³, min radius 0.5×T
Hot rolled — K 0.42, 0.2836 lb/in³, min radius 1×T
Galvanized — K 0.42, 0.2836 lb/in³, min radius 1×T
316 / 316L — K 0.45, 0.2890 lb/in³, min radius 0.5×T
Copper — K 0.38, 0.3230 lb/in³
Brass — K 0.38, 0.3080 lb/in³
Titanium Gr 2 — K 0.35, 0.1630 lb/in³, min radius 3×T
Where These Numbers Meet Real Tooling
A calculator gives you a number. A press brake gives you a part. The gap between them is tooling, temper, grain direction and operator judgment, and that gap is why we check every flat pattern against the equipment we actually run before anything gets cut.
MJM Manufacturing runs nine Amada press brakes in Miami Gardens, FL, including a 240-ton, 14-foot HRB 2204 for long structural bends, plus three Knuth plate rollers at three, four and seven feet for rolled sections. Cutting runs on five Amada fiber lasers — a Ventis 3015AJ 4kW with Locus Beam Control, three Ensis 3015AJ 3kW machines and an LC2415 A III — supported by three CSD nitrogen generators producing 99.9999% nitrogen for oxide-free edges on stainless and aluminum. We cut mild steel to 1 inch, stainless and aluminum to 5/8 inch, and copper and brass to 3/8 inch. Formed parts hold roughly ±0.5° on angle and ±0.010 inch on flange, with laser-cut features at roughly ±0.005 inch.
Verification is not a formality here. An Amada Fabri-Vision 24-camera system inspects flat parts against the CAD file, and Keyence LM-X and XM-5000 coordinate measuring equipment handles formed geometry. When a flat pattern comes back a few thousandths off across a bank of bends, that is where we catch it — before it becomes a hundred parts.
If you are still early in the design, send the model rather than a finished print. Our team reviews radii, hole placement, flange heights and hardware clearance and tells you what to change to bring the cost down. That review is how our prototyping work runs, and it carries straight into production without re-tooling. For forming-specific capability, see precision forming and press brake services.
Sheet Metal Calculator FAQ
Ran The Numbers? Let Us Build It.
Send us a model or a print and we will review the flat patterns, radii and feature spacing against our tooling, then quote it. 47 years, 44,000 square feet and 40+ machines in Miami Gardens, FL.