Calculator Inputs
Example Data Table
| Material | Mass | Volume | Density (kg/m³) | Unit Weight (kN/m³) |
|---|---|---|---|---|
| Concrete (normal) | 2400 kg | 1.00 m³ | 2400 | 23.54 |
| Water | 1000 kg | 1.00 m³ | 1000 | 9.81 |
| Steel | 7850 kg | 1.00 m³ | 7850 | 76.99 |
| Compacted sand | 1700 kg | 1.00 m³ | 1700 | 16.67 |
Formula Used
Mass density is computed as
ρ = m / V,
where m is mass and V is volume.
Unit weight (often called unit density in field practice) is computed as
γ = W / V,
where W is weight.
When mass is provided, weight is calculated using W = m × g with
g = 9.80665 m/s². Unit conversions are applied before final reporting.
How to Use This Calculator
- Select whether you have mass or weight measurements.
- Enter the measured value and choose its unit.
- Enter the measured volume and select its unit.
- Choose output units for density and unit weight.
- Click Calculate to see results above the form.
- Use Download CSV or Download PDF to export your latest result.
Technical Notes
1) Why unit density matters on site
Unit density (mass density) and unit weight help convert volume takeoffs into loads, truck counts, and crane picks. Designers also use density to estimate dead loads, buoyancy, and hydrostatic stability for coastal and marine work. In earthworks, realistic density values improve compaction control and settlement expectations.
2) How it is measured in practice
In the lab, density is obtained from a weighed specimen and a calibrated volume, such as a mold, cylinder, or pycnometer for fine materials. In the field, crews may measure mass with scales and volume from container dimensions, or infer volume from displacement. Always record temperature and moisture condition because they shift results. Tare containers, avoid spillage, and repeat two trials for confidence.
3) Typical reference ranges
Normal concrete often falls near 2300–2500 kg/m³, while structural steel is about 7850 kg/m³. Fresh water is near 1000 kg/m³, and compacted granular fills frequently range from 1600–2200 kg/m³ depending on gradation and compaction. Asphalt mixes are commonly around 2200–2450 kg/m³. Use these values as checks, not as replacements for project testing.
4) Controlling error and variability
Most mistakes come from inconsistent units and poor volume measurement. Convert all inputs to a single base system before calculating. For irregular samples, avoid estimated volumes; use displacement or standardized molds. Remove trapped air, clean containers, and verify the measuring vessel with water. If weight is measured, keep gravity consistent for reporting and compare like-for-like units.
5) Reporting for quality and compliance
Report density with the measurement method, moisture state (dry, SSD, saturated), and sample identification. When comparing to specifications, match the same unit basis and condition. Use the downloadable report to capture inputs, conversions, and final units so reviewers can audit the calculation quickly. Clear records support pay quantities and acceptance decisions consistently.
FAQs
1) What is the difference between density and unit weight?
Density is mass per volume (ρ). Unit weight is weight per volume (γ), equal to ρ × g. They are numerically different because unit weight includes gravity.
2) When should I use the weight input option?
Use it when your measurement comes from a scale or load cell reading in force units, or when you already have a known weight for a container or truck segment.
3) How does moisture change unit density?
Water fills voids and adds mass without much volume change, so wet materials usually show higher density. Report the moisture condition (dry, SSD, saturated) to make comparisons meaningful.
4) Why does the calculator assume standard gravity?
Standard gravity provides consistent reporting across projects and unit systems. If your specifications require local gravity or calibrated force equipment, adjust the input method and document the basis in notes.
5) Can I calculate density from liters or cubic feet?
Yes. Select the matching volume unit, enter your volume, and the calculator converts it internally to cubic meters before computing density and unit weight, then converts back to your chosen outputs.
6) What is pcf and where is it used?
pcf means pounds per cubic foot. It is common in building and geotechnical work in U.S. customary practice for material unit weight and for estimating loads from volume-based quantities.
7) How can I reduce calculation errors?
Measure volume carefully, tare containers, and keep units consistent. Repeat readings, avoid trapped air for fine materials, and compare the result against typical ranges to catch input mistakes early.