Sizing a press brake comes down to two numbers chosen together: tonnage (the force) and length (the bed). Get them right and the machine covers your work for years. Get them wrong and you either cannot make your parts or you pay for capacity you never use.
Tonnage is the force the machine applies. As a rule of thumb for air bending mild steel, a press brake needs roughly 7 to 8 tons per metre of bend for each millimetre of thickness, with the die opening about eight times the thickness. So a 3 mm bend over 2 metres needs far more tonnage than the same bend over half a metre. Stainless and high-strength steel need more force, so size up for them, and always confirm with a tonnage chart or a bend calculator.
Bed length is set by the longest bend you make, plus a margin for the backgauge. Do not buy a very long bed just to bend small parts occasionally, since length costs money and floor space. If long parts are rare, a shorter machine plus occasional outsourcing is often smarter.
Say your heaviest regular job is 4 mm mild steel bent over 2.5 metres. At roughly 7.5 tons per metre per millimetre, that is about 4 x 7.5 x 2.5, near 75 tons for that bend, so a machine around 100 tons with a 3 metre bed gives you headroom. Use the VICLA calculators to confirm for your exact material and die.
Oversizing wastes money and can mark thin parts; undersizing caps the work you can take. Size to your real heaviest and longest parts, add a sensible margin, and no more.
The SUPERIOR hybrid range spans roughly 50 to 320 tons and 2 to 7 metre beds, while the compact FIRST covers light, small-part work. Start from your parts, then match the machine. See the VICLA press brakes.
Use the 7 to 8 tons per metre per millimetre rule as a start, then confirm with a tonnage chart or calculator.
A reasonable margin is wise, but do not oversize on parts you may never make.
Yes, longer bends need more tonnage, so they are chosen as a pair.