Convert between imperial and metric units for asphalt and pavement projects. Area, length/thickness, weight, and density conversions in one place.
The US uses imperial units (ft, in, lb, tons) while most of the world uses metric (m, mm, kg, tonnes). This tool bridges both systems for pavement engineers.
2.3 t/m³ = 143.6 lb/ft³ | 1 in = 25.4 mm | 1 short ton = 2000 lb = 0.907 metric tonnes.
1 sq ft = 0.0929 m² | 1 sq yd = 0.836 m² | 1 short ton = 0.907 metric tonnes | 1 km = 0.621 miles.
Key conversion factors used in asphalt and bitumen project calculations.
| From | To | Multiply By | Category |
|---|---|---|---|
| 1 sq ft | m² | 0.0929 | Area |
| 1 sq yd | m² | 0.8361 | Area |
| 1 m² | sq ft | 10.764 | Area |
| 1 inch | mm | 25.4 | Length |
| 1 mm | inches | 0.03937 | Length |
| 1 foot | m | 0.3048 | Length |
| 1 mile | km | 1.6093 | Length |
| 1 short ton (US) | metric tonnes | 0.9072 | Weight |
| 1 metric tonne | short tons | 1.1023 | Weight |
| 1 lb/ft³ | kg/m³ | 16.018 | Density |
| 1 kg/m³ | lb/ft³ | 0.0624 | Density |
| 145 lb/ft³ | kg/m³ | 2323 | Standard HMA |
The most commonly needed conversion factors in pavement engineering — bridging US imperial specifications and SI metric standards used internationally.
US → Metric: sq ft × 0.0929 = m². A 10,000 sq ft car park = 929 m². For sq yd to m²: sq yd × 0.8361. Metric → US: m² × 10.764 = sq ft. A 1,000 m² road section = 10,764 sq ft = 1,196 sq yd. This conversion is needed when feeding US takeoffs into metric quantity calculators or comparing international project quotes.
Multiply inches by 25.4 to get mm. Common pavement depths: 1.5 in = 38 mm; 2 in = 51 mm; 3 in = 76 mm; 4 in = 102 mm; 6 in = 152 mm. Divide mm by 25.4 to get inches: 50 mm = 1.97 in; 75 mm = 2.95 in; 100 mm = 3.94 in. This is the most frequent manual error source when switching between US and metric asphalt specs.
Short tons × 0.9072 = metric tonnes. Metric tonnes × 1.1023 = short tons. Example: A plant quotes 500 metric tonnes → 500 × 1.1023 = 551.2 short tons. Density: lb/ft³ × 16.018 = kg/m³. Standard HMA 145 lb/ft³ × 16.018 = 2,323 kg/m³. For full tonnage calculations, use the Metric Calculator or Square Feet Calculator.
Use imperial (ft, in, short tons) for US domestic projects, AASHTO-based designs, and state DOT contracts. Use metric (m, mm, metric tonnes) for Australian, New Zealand, European, African, and most international projects. Many multinational projects specify both — use this converter to reconcile quantities between your imperial takeoffs and metric supplier quotes.
Unit conversion errors are among the most common (and costly) mistakes in asphalt procurement. These are the three scenarios where this tool is most critical.
Engineers and estimators working on projects that span multiple countries or use specification documents from different standards bodies often receive area measurements in sq yd, thicknesses in mm, and weights in short tons — all in the same document. This converter allows instant reconciliation, ensuring that the material order placed with a metric supplier matches the imperial dimensions in the design drawings. Errors in this step have caused multi-hundred-thousand dollar over-orders on infrastructure projects.
Related: Metric Calculator
A US-based paving contractor bidding on a project in Canada, Australia, or the UK needs to convert their imperial takeoffs to metric tonnes for supplier quotes. This tool converts sq ft areas and inch thicknesses to m² and mm for metric plant ordering, then converts the resulting metric tonne quote back to short tons for the US bid document. It eliminates the two-step manual conversion chain that causes systematic errors in international procurement.
Related: Tonnage Calculator
Civil engineering students, graduate engineers, and PE exam candidates regularly need to convert between imperial and metric pavement units for design problems. The density conversion between lb/ft³ and kg/m³ (multiply by 16.018) and the sq ft to m² conversion (multiply by 0.0929) are standard exam topics. This reference tool provides instant verification of manual conversion work and a quick sanity check for student pavement design assignments.
Related: Thickness Calculator
Apply your converted values in these quantity calculators.
Choose from area, length/thickness, weight, or density conversions. Area conversions cover square feet, square yards, square metres, and hectares. Thickness conversions handle inches to millimetres and vice versa. Weight conversions cover short tons, long tons, metric tonnes, and kilograms — the four units most commonly quoted in asphalt procurement globally.
Type the value you want to convert in the input field for your source unit. Conversions are instant — results update as you type. Use this to sanity-check contractor quotes, reconcile spec sheets mixing imperial and metric units, or translate measurements from overseas project partners.
The tool displays equivalent values in all related units simultaneously, so you don't need to convert twice. Copy the result you need into your project spreadsheet or tender document. For full asphalt quantity estimates, use the output value in one of our dedicated quantity calculators (square metres, square feet, tonnage, or road calculator).
Multiply inches by 25.4 to get millimetres. Common conversions for asphalt work: 1 inch = 25.4 mm, 1.5 inches = 38 mm, 2 inches = 50.8 mm, 3 inches = 76.2 mm, 4 inches = 101.6 mm. US and Canadian specs typically use inches, while Austroads, NZTA, and European standards use millimetres. This measurement converter handles all these cases instantly without manual arithmetic.
One square yard equals 0.836 square metres. To convert SY to m², multiply by 0.836 (or divide by 1.196). US DOT bid documents often express pavement area in SY, while metric countries use m². If you receive a road project area in SY and need to order from a metric supplier, this converter bridges the gap without error-prone manual calculation.
A US short ton = 2,000 lb (907.2 kg). A UK long ton = 2,240 lb (1,016 kg). A metric tonne = 1,000 kg (2,204.6 lb). In asphalt procurement, the US uses short tons, Australia and Europe use metric tonnes, and the UK has largely switched to metric tonnes for road work. Confusing these units on a large project can cause a 10–12% material over- or under-order, so always confirm the unit convention with your supplier.
Divide lb/ft³ by 62.428 to get t/m³ (metric tonnes per cubic metre). So 145 lb/ft³ ÷ 62.428 ≈ 2.32 t/m³. In reverse, multiply t/m³ by 62.428 to get lb/ft³. This conversion matters when switching between imperial and metric quantity calculators or when comparing mix design data from different countries.
Multiply miles by 1.6093 to get kilometres. One mile = 1,609.3 metres. For a 5-mile road resurfacing project: 5 × 1.6093 = 8.047 km = 8,047 metres. Common US highway project quantities are expressed in lane-miles; multiply by 1.6093 to get lane-kilometres for metric procurement. A 24-ft (7.3 m) wide, 5-mile road = 8,047 m × 7.3 m = approximately 58,743 m² of paving area — convert this to tonnes using the Square Metres Calculator.
Multiply lb/yd³ by 0.5933 to get kg/m³. Standard HMA at 145 lb/ft³ = 3,915 lb/yd³ = 3,915 × 0.5933 = 2,323 kg/m³. Alternatively, convert lb/ft³ to kg/m³ directly by multiplying by 16.018. The lb/yd³ unit occasionally appears on US DOT specifications when expressing mix design Marshall properties or volumetric data. For a complete reference of all density conversions with instant calculation, use the Density Converter tool above.
Multiply kg/m² by the area in m², then divide by 1,000 to get metric tonnes. Example: a 50 mm layer at 2,350 kg/m³ = 117.5 kg/m². For a 2,000 m² project: 117.5 × 2,000 ÷ 1,000 = 235 metric tonnes. The kg/m² unit is commonly used in Austroads and NZTA specifications as a simple coverage rate check on site — supervisors can verify delivery dockets against the design kg/m² rate without needing the full volume calculation. For full area-to-tonnage estimation, use the Square Metres Calculator.