Weight Conversions Calculator
Convert between metric and imperial weight units. Calculate bag quantities for cement, sand, gravel, and other construction materials. Includes bulk bag sizing and material density conversions.
Weight in Construction
Accurate weight calculations are essential for ordering materials, estimating transport costs, ensuring structural load calculations, and calculating material quantities from volumes.
Standard Bag Sizes
| Material | Standard Size | Coverage/Use |
|---|---|---|
| Cement | 25kg or 50kg | Mortar, concrete, render |
| Plaster | 25kg | ~10m² at 2mm |
| Sand (small) | 25kg | Small jobs, mortar |
| Sand (large) | 40kg | Better value bulk |
| Postcrete | 20kg | ~1 post per bag |
| Mortar Mix | 25kg | ~25 bricks |
Bulk Bag (Ton Bag) Sizes
| Type | Weight | Volume | Best For |
|---|---|---|---|
| Mini Bulk | 250kg | ~0.15m³ | Small projects |
| Standard Bulk | 850kg | ~0.5m³ | General use |
| Jumbo Bulk | 1000kg (1 tonne) | ~0.6m³ | Best value |
| Large Bulk | 1500kg | ~0.9m³ | Large projects |
Material Densities
Convert between volume and weight using material densities:
| Material | Density (kg/m³) | 1m³ weighs |
|---|---|---|
| Cement (dry) | 1,440 | 1.44 tonnes |
| Sand (dry) | 1,600 | 1.6 tonnes |
| Sand (wet) | 1,900 | 1.9 tonnes |
| Gravel | 1,700 | 1.7 tonnes |
| Ballast | 1,750 | 1.75 tonnes |
| Topsoil | 1,200 | 1.2 tonnes |
| Concrete | 2,400 | 2.4 tonnes |
| Steel | 7,850 | 7.85 tonnes |
Weight Conversion Reference
| Metric | Imperial |
|---|---|
| 1 kg | 2.205 lb |
| 1 tonne | 0.984 long tons (UK) |
| 1 tonne | 1.102 short tons (US) |
| 6.35 kg | 1 stone |
| 50.8 kg | 1 cwt (hundredweight) |
Wastage Allowances
Always add wastage when ordering materials by weight:
- Cement: 5-10% wastage
- Sand/Gravel: 5-10% wastage
- Loose materials: 10-15% wastage
- Pre-mixed: 5% wastage
UKUK Building Regulations
References & Sources
Standards Cited
- NIST Handbook 44 — Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices
Provides authoritative conversion factors between imperial and metric weight units (e.g., 1 lb = 0.453592 kg) View → - BS EN 1991-1-1 — Eurocode 1: Actions on structures — Part 1-1: Densities, self-weight, imposed loads
Source of standard material densities used for volume-to-weight conversions (e.g., dry sand 1600 kg/m³, concrete 2400 kg/m³)
Formulas Used
- Weight Unit Conversion:
result = value x (fromFactor / toFactor)
Source: NIST Handbook 44 — Conversion via kilograms as the intermediate base unit - Bags Required:
bags = ceil(totalWeight x (1 + wastage%) / bagSize)
Source: Construction industry practice — Default 5% wastage allowance - Volume to Weight:
weight (kg) = volume (m³) x density (kg/m³)
Source: BS EN 1991-1-1 - Weight to Volume:
volume (m³) = weight (kg) / density (kg/m³)
Source: BS EN 1991-1-1
Key Assumptions
- Standard cement bag size of 25 kg (UK standard) — Manufacturer industry standard (UK)
- Standard bulk bag (jumbo bag) holds 1000 kg — Manufacturer industry standard
- Dry sand density of 1600 kg/m³ — BS EN 1991-1-1 Table A.1
- Dry cement density of 1440 kg/m³ — BS EN 1991-1-1
- Default 5% wastage allowance for bagged materials — Construction industry standard practice
- 1 UK long ton = 1016.05 kg — NIST Handbook 44