Press Brake Tonnage: How to Calculate What You Actually Need

Buying a press brake without calculating required tonnage is one of the most common — and costly — mistakes in fabrication equipment purchasing. Too little tonnage and the machine can't form your material. Too much and you've spent $40,000–$80,000 extra on capacity you'll never use.

The basic tonnage formula

Required tonnage = (Material tensile strength × Material thickness² × Bend length) ÷ (Die opening width × 5.33)

For mild steel (tensile strength 60,000 PSI), 10 gauge (0.134"), 48" bend length, 1" V-die opening: (60,000 × 0.018 × 48) ÷ (1 × 5.33) = approximately 9.7 tons per foot, or 38.7 tons total.

Material tensile strength values

• —Mild steel (A36): 58,000–80,000 PSI — use 60,000 for estimates
• —Stainless steel (304): 75,000–95,000 PSI — use 90,000; requires 50% more tonnage than mild steel
• —Aluminum (6061-T6): 40,000–45,000 PSI — use 42,000
• —Hot-rolled steel: Similar to mild steel at equivalent thickness
• —High-strength steel (HSLA): Can reach 100,000+ PSI — verify with mill cert

Add a safety margin

Never buy a press brake rated exactly at your calculated tonnage. Material varies — a sheet certified at 60,000 PSI tensile might test at 65,000 PSI. V-die selection changes requirements. Running the machine at 100% rated tonnage reduces component life significantly.

Rule of thumb: buy a machine rated for 20–30% more tonnage than your peak calculated requirement. If your most demanding job calculates to 80 tons, buy a 100-ton machine.

Bed length matters as much as tonnage

A 100-ton machine with a 10' bed lets you distribute force across the full bed length. If you bend short parts on a long machine, you're applying 100 tons over 24" instead of 120" — creating concentrated force that can damage the machine. Match bed length to your most common part length, not your longest part.

VTM CNC Press Brake range

Our CNC hydraulic press brakes range from 40 ton/4' to 400 ton/14'. All come with the Delem DA-66T controller, 4-axis back gauge, and ±0.01mm repeatability. We'll help you spec the right machine for your material mix before you commit to a purchase.