Bitumen
Bitumen Grades Explained: 40/60 vs 60/70 vs 80/100
The numbers in a bitumen grade are not arbitrary — they describe hardness, and hardness is what determines whether your road survives its local climate.
Penetration grades (40/60, 60/70, 80/100, 85/100) are the most common way bitumen is classified worldwide, but the numbers themselves confuse a lot of people the first time they see them. They are not a percentage, a ratio of materials, or a price tier — they describe how hard or soft the bitumen is.
What the numbers actually mean
The grade comes from the "penetration test": a standard needle, under a fixed 100g load, is lowered into a sample of bitumen at 25°C for 5 seconds, and the depth it penetrates is measured in tenths of a millimetre. A 60/70 grade bitumen allows the needle to penetrate between 60 and 70 (i.e., 6.0–7.0mm). The lower the number, the harder the bitumen; the higher the number, the softer it is.
| Grade | Hardness | Typical Climate | Common Use |
|---|---|---|---|
| 30/40 | Very hard | Very hot / high-traffic | Heavy-duty highways, airport runways in hot regions |
| 40/60 | Hard | Hot climates | High-traffic roads, binder courses in warm regions |
| 60/70 | Medium | Temperate / moderate | General-purpose paving, the most widely used grade globally |
| 80/100 | Soft | Cold / temperate climates | Wearing courses in colder regions, better low-temperature flexibility |
| 85/100 & 100/120 | Very soft | Cold climates | Surface dressing, cold-weather resilience, crack resistance |
Why climate decides the grade, not preference
Hot climates need harder bitumen (lower penetration number) because heat softens bitumen further — use a soft grade in a hot region and the road will rut and shove under traffic in summer. Cold climates need softer bitumen (higher penetration number) because cold makes bitumen brittle — use a hard grade in a cold region and the pavement will crack under thermal contraction and traffic loading in winter. This is why the same road specification can call for completely different grades in Phoenix versus Minneapolis, or Lahore versus Islamabad in winter.
Grade affects density — which affects your calculator inputs
Different grades have marginally different densities (typically 1000–1050 kg/m³ at 15°C), and the difference compounds over large volumes. Always use the density figure from your supplier’s data sheet for the specific grade you are ordering, not a generic average.
Other classification systems you may encounter
Penetration grading is the most widely used system globally. In North America, the Superpave Performance Grade (PG) system is dominant instead — grades like PG 64-22 describe the high and low temperature the binder is engineered to withstand (64°C max pavement temp, -22°C min). Viscosity grading (AC-20, AC-30, etc.) is an older US system still referenced in some specs, and a small number of countries use their own national viscosity-grading standards (for example VG-10 through VG-40) alongside or instead of penetration grading. If your project specification cites a grading system your supplier doesn’t normally quote, ask for a cross-reference rather than assuming a direct substitute — these systems measure different properties and don’t always convert one-to-one without lab data.
Finding the right grade for your location
Grading systems and standard grades are set nationally or regionally, not globally, so the fastest way to confirm what you need is to check your local road authority’s standard specification or ask your bitumen supplier what grade they stock as default for general paving in your area. Most suppliers will already know the standard grade for local climate and traffic conditions — treat this guide as background for understanding what the grade means, not a substitute for your project’s actual specification.
Once you know your grade, plug the correct density into the calculator