How do you calculate casting weight variation?

Subtract the lowest measured casting weight from the highest to get the spread, then compare the midpoint of those two to the nominal weight for the bias delta. With a 24.8 lb high and 23.9 lb low entered, the calculator returns the spread directly from those readings.

What is an acceptable casting weight variation?

It depends on part size and process, but many foundries hold gray-iron castings within roughly 1 to 3% of nominal weight. On a 24.2 lb nominal that is about 0.24 to 0.73 lb of total spread; tighter for machined-critical parts, looser for rough sand castings.

What does weight spread tell me about my process?

A widening spread usually means inconsistent shrinkage, drifting core position, variable gating fill, or flash. It is an early warning that dimensional defects may follow before they show up in machining or inspection.

What is the difference between spread and delta to nominal?

Spread is scatter — how far apart your castings are from each other. Delta to nominal is bias — whether the whole batch trends heavy or light versus design. You can have a tight spread that is biased heavy, which wastes metal even though the parts are consistent.

Why would heavier castings be a problem if they pass dimensionally?

Extra weight is extra metal poured, which lowers yield and raises cost per part. A persistent heavy bias also often masks oversize cores or excess flash that will eventually drift into a dimensional reject.

How many castings should I weigh to judge variation?

For a meaningful range you want a representative sample across the run, not just two parts. The high-minus-low method here is a quick check; for control use a larger sample with standard deviation or an SPC chart.

Foundry & Forging calculator

Casting Weight Variation Calculator

Casting weight variation measures how much the weight of nominally identical castings spreads from heaviest to lightest, and how far the center of that spread sits from the design nominal. Quality engineers and process controllers in foundries and forges use it as a fast proxy for dimensional and metal-yield consistency, because weight drift usually signals shifting core position, gating, shrinkage, or flash. It matters because excess weight variation eats metal yield, hints at incipient dimensional defects, and can push parts out of customer weight tolerance. This calculator returns both the raw spread and the midpoint-to-nominal delta so you can separate scatter from bias.

What this calculator does

Compare casting weight spread against nominal casting weight to monitor process variation.
Use it when pattern wear, sand compaction, core shift, gating changes, machining stock, or metal feed affects casting weight consistency.
It computes the weight range (highest minus lowest) and the delta of the sample midpoint to the nominal casting weight.

Formula used

Casting Weight Variation range = highest casting weight measured - lowest casting weight measured
Casting Weight Variation delta to target = midpoint - nominal casting weight

Inputs explained

Highest casting weight measured:
Lowest casting weight measured:
Nominal casting weight:

How to use the result

Use it on a sampling cadence during a run to catch process drift early, or when investigating a yield or dimensional complaint.
Range from only two extreme values is a coarse measure; it ignores distribution shape and sample size, so pair it with standard deviation or SPC for a real capability picture.

Current U.S. benchmarks

The producer price index for steel mill products stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 3,569 primary metal manufacturing establishments employing about 354,911 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate casting weight variation? Subtract the lowest measured casting weight from the highest to get the spread, then compare the midpoint of those two to the nominal weight for the bias delta. With a 24.8 lb high and 23.9 lb low entered, the calculator returns the spread directly from those readings.
What is an acceptable casting weight variation? It depends on part size and process, but many foundries hold gray-iron castings within roughly 1 to 3% of nominal weight. On a 24.2 lb nominal that is about 0.24 to 0.73 lb of total spread; tighter for machined-critical parts, looser for rough sand castings.
What does weight spread tell me about my process? A widening spread usually means inconsistent shrinkage, drifting core position, variable gating fill, or flash. It is an early warning that dimensional defects may follow before they show up in machining or inspection.
What is the difference between spread and delta to nominal? Spread is scatter — how far apart your castings are from each other. Delta to nominal is bias — whether the whole batch trends heavy or light versus design. You can have a tight spread that is biased heavy, which wastes metal even though the parts are consistent.
Why would heavier castings be a problem if they pass dimensionally? Extra weight is extra metal poured, which lowers yield and raises cost per part. A persistent heavy bias also often masks oversize cores or excess flash that will eventually drift into a dimensional reject.

Last reviewed 2026-05-12.