kilograms per cubic meter (kg/m3) to tonnes per cubic meter (t/m3) conversion

What is the Kilogram per Cubic Meter?

The kilogram per cubic metre is the SI derived unit of density (mass per unit volume). It expresses how much mass is contained within a one-cubic-metre volume of a substance.

Definition

One kilogram per cubic metre is one kilogram of mass distributed uniformly through one cubic metre of space. It is the SI base-unit expression of density and therefore its own ground truth.

$$1\ \text{kg/m}^3 = 1\ \text{kg/m}^3$$

Because it combines the base units kilogram and metre directly, it needs no conversion factor within the SI system.

Origin and History

The unit follows directly from the metre-kilogram-second (MKS) system adopted as the foundation of the modern International System of Units (SI) in 1960. Density as mass per volume was formalised through the work of Archimedes on buoyancy and later quantified precisely once the kilogram and metre were standardised in the late 18th and 19th centuries.

Law and Notable Facts

The kilogram per cubic metre is the coherent SI unit for density and is legally recognised worldwide. It is numerically identical to the gram per litre and to the milligram per millilitre, all three equalling one another exactly. Everyday materials are often quoted in the equal but more convenient g/cm³, where 1 g/cm³ = 1000 kg/m³.

Real-World Examples and Conversions

• Pure water at 4 °C has a density of about 1000 kg/m³.
• Dry air at sea level and 15 °C is roughly 1.225 kg/m³.
• Iron is about 7870 kg/m³, and lead about 11340 kg/m³.
• 1 kg/m³ = 0.001 g/cm³ = 1 g/L = 1 mg/mL.

What is the Tonne per Cubic Meter?

The tonne per cubic meter is a metric unit of mass density, giving the number of metric tonnes of mass contained in one cubic meter of volume. It is common in civil engineering, mining, and bulk-materials handling, where masses are large.

Definition

One tonne per cubic meter equals one metric tonne (1000 kilograms) spread over one cubic meter. In SI base units:

$$1\ \text{t/m}^3 = 1000\ \text{kg/m}^3$$

This makes the tonne per cubic meter numerically equal to the kilogram per liter and to the gram per cubic centimeter, so pure water is very close to 1 t/m³.

Origin and History

The metric tonne (1000 kg) was adopted alongside the metric system to handle industrial-scale masses, and pairing it with the cubic meter—the coherent SI unit of volume—produced a convenient large-scale density unit. It became standard in continental European engineering practice during the nineteenth and twentieth centuries.

Law and Notable Facts

The tonne is accepted for use with the SI, though "t/m³" is a derived combination rather than a coherent SI unit itself. A handy fact: because 1 t/m³ equals 1 kg/L, an engineer's "specific gravity" of a material relative to water reads directly as its density in t/m³.

Real-World Examples and Conversions

Fresh water is about 1.00 t/m³ and seawater about 1.025 t/m³. Ordinary structural concrete runs roughly 2.4 t/m³, while structural steel is about 7.85 t/m³. Dry loose sand is around 1.6 t/m³. To convert to pounds per cubic foot, multiply by 62.43.