Skip to content
ENExplore Calculators

Runner And Riser Sizing Calculator

Work out runner and riser sizing instantly with clear inputs, formula shown and shareable results.

About Runner And Riser Sizing Calculator

A riser must hold enough liquid metal to feed solidification shrinkage, conventionally 20-30 percent of the casting volume, and be shaped so it freezes last: a height to diameter ratio of about 1.5 gives that. The gating system is proportioned to an unpressurised 1:2:2 ratio of sprue choke to runner to ingates so the mould fills without turbulence.

Formulas

Riser volume

Riser cm³ = casting volume x riser fraction

Riser diameter

D = (4V / (pi x 1.5))^(1/3) for H = 1.5 D

Gating ratio

Sprue : runner : ingates = 1 : 2 : 2 for an unpressurised system

Worked example

With the default values below, Runner And Riser Sizing Calculator returns Riser volume required of 625.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Casting volumeminimum 1 cm³
2,500 cm³
Riser volume as share of castingaccepts 5–100 %
25 %
Sprue choke areaminimum 0.1 cm²
3 cm²

Results

Riser volume required
625.0 cm³
Riser diameter at 1.5:1 height ratio
8.10 cm
Runner area at 1:2:2 gating
6.00 cm²
Total ingate area
6.00 cm²

Step by step

  1. 1Values used
  2. 2Riser volume
  3. 3Riser diameter
  4. 4Gating ratio
  5. 5Riser volume required= 625.0 cm³
  6. 6Riser diameter at 1.5:1 height ratio= 8.10 cm
  7. 7Runner area at 1:2:2 gating= 6.00 cm²
  8. 8Total ingate area= 6.00 cm²

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Runner And Riser Sizing figure worked out?

Riser cm³ = casting volume x riser fraction. A riser must hold enough liquid metal to feed solidification shrinkage, conventionally 20-30 percent of the casting volume, and be shaped so it freezes last: a height to diameter ratio of about 1.5 gives that.

Why an unpressurised gating ratio?

Enlarging the runner and ingates downstream of the choke slows the metal and keeps the system full but not jetting, which reduces air entrainment and dross in the casting.

What values do I need to enter?

This calculator takes 3 inputs: Casting volume, Riser volume as share of casting, Sprue choke area. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

Related Calculators

Runner And Riser Sizing Calculator | Calcrivo