Extrusion Ratio Calculator

What extrusion ratio means, and how to use it

The extrusion ratio (ER) compares the cross-sectional area of the container (what goes in) to the total cross-sectional area of the profile coming out of the die (what comes out):

ER = Container area ÷ (Number of cavities × Profile area per cavity)

A ratio of 30:1 means the metal's cross-section is squeezed down to 1/30th of its original size as it passes through the die. It's a single number, but it tells you a lot about how a die and press combination will behave:

• Higher ratio → more deformation, higher breakthrough pressure, generally slower exit speed, but usually better surface finish and grain structure.
• Lower ratio → less pressure needed, faster extrusion, but coarser grain and, below a certain point, a higher risk of surface tearing or poor bonding on hollow profiles.

Typical practical ranges by alloy

These are the ranges most plants work within — not hard limits. Actual practical maximums depend on your press capacity, billet temperature, container condition and how complex the profile is.

A few things worth knowing before you rely on the number

• ER is based on container bore area, not billet diameter — the billet upsets to fill the container in the first moments of the stroke, so container ID is what matters.
• For multi-hole dies, use the combined area of all cavities — that's the real ratio the press has to work at.
• A very low ratio (say, under 10 for 6xxx) can be as troublesome as too high a ratio — thick, simple sections extruded at low ratios can have coarser, less uniform grain structure and worse surface finish.
• This tool gives you the geometric ratio. Whether it's actually achievable on your press also depends on tonnage, billet temperature, and die design — always validate with a trial or your process engineer for new dies.