Reliable weight estimates are essential for nickel-alloy RFQs, freight planning, machining yield and cost comparison. Density varies by alloy chemistry, while ordered and shipped weight also includes mill tolerance, machining allowance, scale, packaging and cut loss. Use the chart for estimates and the actual certified or measured weight for commercial settlement.
Important: Densities below are representative manufacturer values rounded for engineering estimates. Composition variation and source rounding can produce small differences. Confirm the governing datasheet when mass is safety-critical.
The Short Answer
Most commercial nickel alloys have densities from about 7.9 to 9.0 g/cm³. Inconel 718 is approximately 8.19 g/cm³, Alloy 625 about 8.44, Monel 400 about 8.80 and Hastelloy C-276 about 8.89. Calculate volume in consistent units, multiply by density, then add manufacturing tolerance and procurement allowance.
Nickel Alloy Density Chart
| Alloy | UNS | Density g/cm³ | Density lb/in³ (approx.) |
|---|---|---|---|
| Nickel 200 / 201 | N02200 / N02201 | 8.89 | 0.321 |
| Monel 400 | N04400 | 8.80 | 0.318 |
| Monel K-500 | N05500 | 8.44 | 0.305 |
| Inconel 600 | N06600 | 8.47 | 0.306 |
| Inconel 601 | N06601 | 8.11 | 0.293 |
| Inconel 625 | N06625 | 8.44 | 0.305 |
| Inconel 718 | N07718 | 8.19 | 0.296 |
| Inconel X-750 | N07750 | 8.28 | 0.299 |
| Incoloy 800/800H/800HT | N08800/N08810/N08811 | 7.94 | 0.287 |
| Incoloy 825 | N08825 | 8.14 | 0.294 |
| Hastelloy B-3 | N10675 | 9.22 | 0.333 |
| Hastelloy C-22 | N06022 | 8.69 | 0.314 |
| Hastelloy C-276 | N10276 | 8.89 | 0.321 |
| Hastelloy X | N06002 | 8.22 | 0.297 |
| Alloy 20 | N08020 | 8.08 | 0.292 |
Use one source consistently within a project. A difference of 0.5% in density is usually smaller than oversized stock or cutting allowance, but it matters for large tonnage.
Unit Conversion
- 1 g/cm³ = 1,000 kg/m³.
- 1 g/cm³ ≈ 0.036127 lb/in³.
- Mass (kg) = volume (m³) × density (kg/m³).
- Mass (lb) = volume (in³) × density (lb/in³).
Never mix millimetres with metres without conversion. For mm dimensions, the compact formulas below return kilograms directly.
Round Bar Weight Formula
For diameter D in mm and length L in mm:
Weight (kg) = π × D² / 4 × L × density (g/cm³) ÷ 1,000,000
Example: Inconel 718 Round Bar
A 100 mm diameter × 2,000 mm long 718 bar:
- Volume = π × 100² / 4 × 2,000 = 15,707,963 mm³.
- Weight = 15,707,963 × 8.19 ÷ 1,000,000.
- Estimated net weight = 128.6 kg.
The quoted gross weight may be higher because the mill supplies diameter and length oversize. See Forged, Rolled or Cold-Drawn Nickel Alloy Bar.
Plate and Sheet Weight Formula
For thickness T, width W and length L in mm:
Weight (kg) = T × W × L × density (g/cm³) ÷ 1,000,000
Example: a 10 × 1,500 × 3,000 mm Alloy 625 plate weighs approximately:
10 × 1,500 × 3,000 × 8.44 ÷ 1,000,000 = 379.8 kg
Plate thickness tolerance and edge trimming can change invoice weight. For ordering details, see the Nickel Alloy Sheet, Plate and Strip Guide.
Hollow Bar and Pipe Formula
For outside diameter OD, inside diameter ID and length L in mm:
Weight (kg) = π × (OD² − ID²) / 4 × L × density ÷ 1,000,000
For nominal pipe, do not calculate from NPS alone. Obtain actual OD and wall thickness from the applicable dimensional standard, calculate ID = OD − 2t, and then apply the formula. Read Nickel Alloy Pipe vs Tube.
Ring Weight Formula
For a rectangular-section ring with OD, ID and axial height H in mm:
Weight (kg) = π × (OD² − ID²) / 4 × H × density ÷ 1,000,000
This is theoretical finished geometry. A forged ring blank includes machining allowance on OD, ID and height. The forging supplier may also quote input billet weight, which includes crop and process loss. See Forged, Rolled and Cut Nickel Alloy Rings.
From Net Weight to Purchase Weight
Add allowances explicitly:
- Mill dimensional tolerance.
- Machining allowance and surface-removal stock.
- Saw kerf and end discard.
- Forging flash, tongue or test prolongations.
- Test coupons and destructive specimens.
- Minimum order quantity and standard mill length.
- Packaging, pallets and corrosion protection for freight.
Do not hide these factors in a large arbitrary percentage. Use actual ordered dimensions for metal weight, then show process yield and packaging separately.
Cost Estimation
Theoretical metal cost is:
Estimated material cost = purchase weight × price per kg
Final price may include melting route, small-lot premium, conversion, heat treatment, testing, machining, certification and alloy surcharge. Two alloys with similar density can have radically different prices; density is not a cost proxy.
RFQ Weight Checklist
- Alloy/UNS and density source.
- Finished and ordered dimensions.
- Positive/negative mill tolerances.
- Quantity and cut length.
- Machining allowance.
- Test coupons or prolongations.
- Net, gross and chargeable weight basis.
- Random or exact lengths.
- Packaging and pallet weight.
- Unit system and rounding rule.
- Commercial weighing method and scale tolerance.
Frequently Asked Questions
What is the density of Inconel 625?
Approximately 8.44 g/cm³ or 0.305 lb/in³ according to manufacturer data.
What is the density of Inconel 718?
Approximately 8.19 g/cm³ or 0.296 lb/in³.
Is Hastelloy heavier than Inconel?
Some grades are. C-276 is about 8.89 g/cm³, while 718 is about 8.19. Compare the exact alloys rather than brand families.
Why does the supplier’s weight differ from my calculation?
The supplier may use actual oversize dimensions, measured weight, longer mill lengths, test stock or packaging. Ask whether the quotation is net, gross or chargeable weight.
Can density confirm alloy identity?
No. Many alloys have overlapping density ranges. Use PMI, chemistry and traceability for identification.
Final Recommendation
Calculate from ordered geometry, use a manufacturer density, and separate net metal, process yield and freight weight. Send J&A Alloy the alloy, form, finished and ordered dimensions, tolerances, quantities, tests and delivery lengths for a traceable weight and price calculation.
