Enter your material, thickness, and cut length. Get the shearing force, the equivalent mild-steel capacity, and the shear size that fits — with the math shown.
Shear strength ≈ 75–80% of tensile strength.
Sizes the bed — barely changes the tonnage (see below).
Steeper rake = less force, but more edge distortion.
Required shearing force
– tons
Equiv. mild-steel thickness
–
Rake used
–
Cut length
–
Shear size that fits
–
The thing that surprises everyone: cut length barely changes the tonnage. Because the blade sits at an angle (rake), only a few inches of material are being cut at any instant — a 1-ft cut needs essentially the same force as a 12-ft cut. Length sizes the bed, not the hydraulics. That's why shears are sold as thickness capacity × length, not tons.
How this is calculated
Shearing force is roughly material shear strength × the area being cut at any instant. Rake shrinks that area to a short section of the blade, which is why length drops out of the equation:
shearing force (lbf) = shear strength × 0.833 × T × (12 × T ÷ rake) tons = force ÷ 2000
Rake in inches per foot sets the instantaneous cut length (12×T ÷ rake). Double the rake, halve the force — but gain edge distortion.
Force ∝ thickness² — doubling thickness quadruples the load, just like a press brake.
Equivalent mild-steel thickness converts your material back to the MS rating every shear is sold by, so you can compare machines directly.
Method follows published shear-capacity engineering data (Cincinnati Incorporated). An estimator — verify against the machine's rating plate.
Common questions
Does cut length change the tonnage a shear needs?
Barely. Because the blade is angled (rake), only a few inches of material are being cut at any instant — a 1-ft cut needs essentially the same force as a 12-ft cut. Length sizes the bed, not the hydraulics.
What rake angle should I run?
The minimum rake that still gives an acceptable edge. More rake means less force but more edge distortion, camber, and demand on the hold-downs. For stainless or work-hardening material, start at maximum rake and reduce it while watching cut quality.
Can I shear stainless on a shear rated for mild steel?
Only thinner stainless. Stainless needs roughly 1.5× the shearing force of mild steel at the same thickness — convert to equivalent mild-steel thickness first. A shear rated 1/4" mild steel handles about 3/16" 304 stainless.
Why is my sheared edge bowed or cambered?
Usually too much rake angle, dull knives, or excessive blade clearance. Reduce rake to the minimum that still cuts cleanly, check knife sharpness, and verify clearance is set for the material thickness.
Fine print. This calculator is an estimator, not engineering advice. Figures assume sharp knives, correct blade clearance, and material at nominal shear strength — real stock varies, knives dull, and machine condition matters. Always confirm against the machine’s rating plate and the manufacturer’s capacity chart before quoting or cutting. Use at your own risk.