K-Factor Calculator (Sheet Metal)
Reverse-engineer the true K-factor of your material and tooling from one measured test bend — flat length, legs, thickness and radius in; K out.
CAD defaults like K = 0.44 are guesses; the K-factor that actually matters belongs to YOUR material, YOUR die and YOUR radius. Bend one coupon, measure both legs to the apex with a caliper, and this calculator hands back the K that makes flat patterns land on size. Materials bent over a sharp die drift toward 0.33; large-radius soft aluminium drifts toward 0.50.
Formula
Note: K varies with the radius-to-thickness ratio — re-run the test when you change die, material lot or grain direction for tight-tolerance flanges.
Reverse-engineer the true K-factor of your material and tooling from one measured test bend — flat length, legs, thickness and radius in; K out. A free machinist & fabrication essentials tool — no sign-up, no upload, instant results in your browser.
About K-Factor Calculator (Sheet Metal)
K-Factor Calculator (Sheet Metal) computes the governing relationship BD = A + B − flat ; BA = 2·(R+T)·tan(θ/2) − BD ; K = (BA/θᵣₐ𝒹 − R) / T live as you type. CAD defaults like K = 0.44 are guesses; the K-factor that actually matters belongs to YOUR material, YOUR die and YOUR radius. Bend one coupon, measure both legs to the apex with a caliper, and this calculator hands back the K that makes flat patterns land on size. Materials bent over a sharp die drift toward 0.33; large-radius soft aluminium drifts toward 0.50. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use K-Factor Calculator (Sheet Metal)
- 1Enter your values — Flat length before bending, Measured leg A (to apex), Measured leg B (to apex), Material thickness and more (sensible defaults are pre-filled).
- 2Read the live results: K-factor, Bend allowance, Bend deduction.
- 3Check the "with your numbers" line to see BD = A + B − flat ; BA = 2·(R+T)·tan(θ/2) − BD ; K = (BA/θᵣₐ𝒹 − R) / T substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use K-Factor Calculator (Sheet Metal)?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula BD = A + B − flat ; BA = 2·(R+T)·tan(θ/2) − BD ; K = (BA/θᵣₐ𝒹 − R) / T with authoritative sources cited on the page (Machinery's Handbook, 31st ed.; Benson, S. — The Fabricator: Analyzing the k-factor in sheet metal bending)
- ✓CAD defaults like K = 0.44 are guesses; the K-factor that actually matters belongs to YOUR material, YOUR die and YOUR radius.
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the k-factor calculator (sheet metal) use?+
It evaluates BD = A + B − flat ; BA = 2·(R+T)·tan(θ/2) − BD ; K = (BA/θᵣₐ𝒹 − R) / T, exactly as published. Sources: Machinery's Handbook, 31st ed.; Benson, S. — The Fabricator: Analyzing the k-factor in sheet metal bending. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
CAD defaults like K = 0.44 are guesses; the K-factor that actually matters belongs to YOUR material, YOUR die and YOUR radius. K varies with the radius-to-thickness ratio — re-run the test when you change die, material lot or grain direction for tight-tolerance flanges.
When is this calculator the right tool for the job?+
Reverse-engineer the true K-factor of your material and tooling from one measured test bend. Bend one coupon, measure both legs to the apex with a caliper, and this calculator hands back the K that makes flat patterns land on size. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
Related tools
- True Position Calculator (GD&T)
- Surface Roughness Converter (Ra ⇄ Rz, RMS, N grade)
- Shrink Fit Temperature Calculator
- O-Ring Groove Calculator (Gland Design)
- Sine Bar Calculator (Gauge Block Stack)
- V-Belt Length Calculator
- Roller Chain Length Calculator
- Tap Drill & Tapping Speed — M4×0.7 in Mild Steel
- Servo & Reducer Sizing — Shoulder (Axis 2)
Related Manufacturing tools
Spindle Speed Calculator — Aluminum 6061
Carbide starting RPM for milling Aluminum 6061: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● LiveSpindle Speed Calculator — Mild Steel 1018
Carbide starting RPM for milling Mild Steel 1018: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● LiveSpindle Speed Calculator — Stainless 304
Carbide starting RPM for milling Stainless 304: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● Live