Hydraulic Press Tonnage Selection: A Practical Guide

Selecting the right tonnage for a hydraulic press is the single most common engineering question our application engineers get from metal-formers. Too little tonnage causes incomplete part formation, excessive spring-back, and tooling damage. Too much wastes capital, energy, and floor space.

This guide walks through the calculation we use with our customers, with worked examples for three common applications.

The required press tonnage for a forming operation is calculated as:

F = p × A × SF

Where:
  F  = required press force (tons or kN)
  p  = material flow stress at the forming temperature (MPa or tons/in²)
  A  = projected area of the part (mm² or in²)
  SF = safety factor (typically 1.2 to 1.5)

For room-temperature forming of mild steel, p ≈ 0.3 kN/mm² (≈ 0.025 tons/in²). For stainless steel it's ~50% higher. For hot forging (>900 °C) it's roughly 1/10th of the room-temperature value.

A 600 × 400 mm sink with 150 mm draw depth, 1.2 mm 304 stainless steel:

• Projected area: 600 × 400 = 240,000 mm²
• Material: 304 stainless at room temperature → p ≈ 0.45 kN/mm²
• Required force: 240,000 × 0.45 = 108,000 kN ≈ 11,000 tons
• With safety factor 1.3: 14,300 tons

In practice, kitchen sinks are made on multi-stage transfer presses rather than single-stroke presses — each stage needs only 25-30% of the total force. So a 1,500-ton press with a 4-stage transfer is typical.

A 400 × 300 mm suspension arm, 4 mm HSLA steel:

• Projected area: 120,000 mm²
• Material: HSLA at room temperature → p ≈ 0.4 kN/mm²
• Required force: 48,000 kN ≈ 4,900 tons
• With safety factor 1.3: 6,400 tons

For automotive components, a 1,000-ton press is typically selected for sub-assemblies, with the main structural parts on larger presses.

• Ignoring draw bead effects: Draw beads add 20-40% to the required force. Most published formulas assume no draw beads.
• Using room-temperature flow stress for warm/hot forming: Flow stress drops sharply with temperature — using the wrong number gives a wildly oversized press.
• No safety factor: Real-world material variation, lubrication inconsistency and tooling wear all push required force higher than the calculated nominal value.
• Forgetting die-opening force: For deep-draw operations, the blank-holder force must be added to the forming force.

Free press sizing consultation

Send us your part drawings, material, draw depth and cycle-time target. Our press application engineers respond with a tonnage recommendation and indicative quote within 24 hours.