---
title: "Iron — density, melting point and properties"
description: "Iron has a density of 7,874 kg/m³. Melting point, strength, conductivity, what it is used for, and whether it floats, rusts or is magnetic."
url: https://atoneplace.net/material/iron/
site: "At One Place"
---

# Iron

**Density of iron: 7,874 kg/m³**

7.87 g/cm³ · 491.6 lb/ft³

Chemically pure iron is barely used — it is soft, and it rusts faster than the steels made from it. Adding 0.2% carbon roughly doubles its strength, which is the entire basis of the steel industry. Its stiffness of 211 GPa is essentially unchanged by alloying, so every steel from a coat hanger to a submarine hull has the same Young's modulus: heat treatment changes strength, never stiffness.

## Properties

- **Density:** 7,874 kg/m³ — 7.87 g/cm³
- **Melting point:** 1,538 °C
- **Tensile strength:** 200–350 MPa
- **Young's modulus:** 211 GPa
- **Thermal conductivity:** 80.4 W/(m·K)
- **Thermal expansion:** 11.8 µm/(m·K)
- **Floats in water:** No
- **Magnetic:** Yes

## What it is used for

- Feedstock for all steelmaking
- Transformer and motor cores (as electrical iron)
- Magnetic shielding
- Laboratory and reference standards

## How it compares

*Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.*

- air: 1.2 kg/m³
- expanded polystyrene foam: 20 kg/m³
- rigid polyurethane foam: 40 kg/m³
- Water — the float line: 1,000 kg/m³
- iron: 7,874 kg/m³
- tungsten: 19,250 kg/m³
- gold: 19,300 kg/m³
- platinum: 21,450 kg/m³

*Water is 1,000 kg/m³. Anything below that floats.*

| Material | Density | Relative to water |
| --- | --- | --- |
| rigid polyurethane foam | 40 kg/m³ | 0.04× |
| expanded polystyrene foam | 20 kg/m³ | 0.02× |
| air | 1.2 kg/m³ | 0.00× |
| iron ← | 7,874 kg/m³ | 7.87× |
| platinum | 21,450 kg/m³ | 21.45× |
| gold | 19,300 kg/m³ | 19.30× |
| tungsten | 19,250 kg/m³ | 19.25× |

## Does it rust?

Yes, and readily. Rust is iron oxide, and it is flaky rather than adherent — it does not seal the surface, so oxygen and water keep reaching fresh metal underneath and the process continues until the section is gone. That non-protective quality is what makes rust different from the oxide layers on other metals.

## Is it magnetic?

Iron, nickel and cobalt are the three common ferromagnetic elements, and anything based mostly on them is strongly attracted to a magnet.

## Common questions

### What is the density of iron?

7,874 kg/m³, or 7.87 g/cm³.

### Does iron float?

No. At 7,874 kg/m³ it is denser than water.

### Is iron magnetic?

Iron, nickel and cobalt are the three common ferromagnetic elements, and anything based mostly on them is strongly attracted to a magnet.

## Related pages

- [Does iron float?](https://atoneplace.net/does-it-float/iron/)
- [Aluminum](https://atoneplace.net/material/aluminum/)
- [Copper](https://atoneplace.net/material/copper/)
- [Gold](https://atoneplace.net/material/gold/)
- [Titanium](https://atoneplace.net/material/titanium/)
- [Lead](https://atoneplace.net/material/lead/)
- [Tungsten](https://atoneplace.net/material/tungsten/)
- [Silver](https://atoneplace.net/material/silver/)
- [Mercury](https://atoneplace.net/material/mercury/)

## Sources

- Wikidata — Wikimedia Foundation (https://www.wikidata.org/) [CC0 1.0]