Stainless Steel Weight per Cubic Inch — Density & Guide

Overview — what "weight per cubic inch" means for stainless steel

"Weight per cubic inch" is simply the mass (in pounds) of one cubic inch of material. For stainless steel this depends on alloy composition and temperature, but for practical shop work and estimation you can use standard density values to compute weight from any measured volume. The direct formula used throughout this article is: weight (lb) = volume (in³) × density (lb/in³). Below you'll find exact conversion factors, commonly-used alloy densities, worked examples, and quick tips for fabrication and estimating scrap or shipping weight.

Standard densities and quick reference table

This table lists commonly-used stainless alloys with their typical density in grams per cubic centimeter (g/cm³), the converted density in pounds per cubic inch (lb/in³), and the resulting weight per cubic foot (lb/ft³). Use the lb/in³ value to multiply by volumes measured in cubic inches.

Conversion factors and the exact formula

Key conversion factors used here (exact values used for the examples):

• 1 g/cm³ = 0.036127292 lb/in³ (use this to convert density in g/cm³ to lb/in³).
• 1 g/cm³ = 62.4279606 lb/ft³ (useful if you prefer working in cubic feet).
• Weight calculation: weight (lb) = volume (in³) × density (lb/in³).

Worked examples (step-by-step)

Example 1 — small part made from 304 stainless, 2.00 in³

Step 1: Use the 304 density in lb/in³: 0.289018 lb/in³. Step 2: Multiply by the part volume: 2.00 in³ × 0.289018 lb/in³ = 0.578036 lb. So a 2.00 cubic-inch 304 piece weighs approximately 0.578 lb.

Example 2 — block sized 3.5 in × 2.0 in × 1.25 in of 316 stainless

First compute volume: 3.5 × 2.0 × 1.25 = 8.75 in³. Use 316 density 0.290102 lb/in³. Multiply: 8.75 in³ × 0.290102 lb/in³ = 2.5373925 lb. Round to practical precision: the block weighs about 2.54 lb.

Temperature, composition, and real-world variations

Published densities are room-temperature nominal values. Factors that cause measurable variation:

• Alloy chemistry: heavier alloying elements (Mo in 316, Ni in austenitics) slightly change density. 316 is marginally denser than 304.
• Porosity or internal voids (castings, sintered parts) reduce effective bulk density relative to the solid value.
• Temperature: thermal expansion reduces density as temperature rises (for precision work use temperature-corrected density).

Practical tips for shop, purchasing, and shipping estimates

Use the following rules-of-thumb and checks when estimating or confirming weight:

• For quick estimates assume 0.29 lb/in³ (good for 304/316 approximations). Multiply by total in³ for fast quotes.
• For large plate orders, convert to lb/ft³ (≈499 lb/ft³ for 304) to compare vendor sheets and freight charges easily.
• When measuring irregular shapes, use displacement (water or oil) to measure volume for precise weight checks, then multiply by density.
• Add a small contingency (1–2%) for coatings, fasteners, or weld material when quoting finished assembly weight.

Precision and how many significant digits to use

Choose precision to match your measurement and application. For shop estimates 2–3 significant digits in pounds is appropriate (e.g., 0.29 lb/in³). For material science or engineering calculations where densities are used in stress or thermal analyses, use manufacturer-specified densities with 4–6 significant digits and include temperature corrections.

Quick conversion cheat-sheet (copyable)

Handy formulas to keep on your phone or notebook:

• Density (lb/in³) = Density (g/cm³) × 0.036127292
• Weight (lb) = Volume (in³) × Density (lb/in³)
• Convert in³ to ft³: ft³ = in³ ÷ 1728

Summary — practical takeaway

For most practical work use 0.289 lb/in³ for 304 stainless and 0.290 lb/in³ for 316 stainless. Multiply those densities by your part volume in cubic inches to get a reliable weight in pounds. For high-precision needs adjust for alloy spec, porosity, and temperature.