---
title: "Hardness, toughness and strength compared"
subject: "Civil Engineering Materials"
chapter: 1
key: "semester_3/civil_engineering_materials:hardness-toughness-strength-difference"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/hardness-toughness-strength-difference
site: BCT Engineering
---

# Hardness, toughness and strength compared

Civil Engineering Materials · Chapter 1: Introduction to Civil Engineering Material

- Asked in: 2081 Chaitra (new course), 3 marks
- Video: [Hardness, Toughness, and Strength | Science Shorts for Grades 8-12 | What's the Difference?](https://www.youtube.com/watch?v=-FgmT1HE7Us) — One Power Company
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/hardness-toughness-strength-difference
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-1

## Question

What is the difference between hardness, toughness and strength of a material? Explain with example.

## Short answer

Hardness is surface resistance to indentation (e.g., glass is hard but brittle). Toughness is energy absorbed before fracture (e.g., mild steel is tough). Strength is maximum stress a material can bear (e.g., high-tensile steel is strong). They are distinct properties.

## Answer

- **Hardness** is resistance to scratching or indentation of the surface.
- **Toughness** is the energy absorbed up to fracture (area under the stress-strain curve).
- **Strength** is the maximum stress a material can carry before failure.

| Basis | Hardness | Toughness | Strength |
|---|---|---|---|
| Meaning | Surface resistance to scratch or indentation | Energy absorption before fracture | Load-carrying capacity per unit area |
| Measure | Mohs, Brinell, Rockwell | Charpy or Izod impact test, area under curve | Stress in $\text{N/mm}^2$ |
| Depends on | Surface/atomic bonding | Strength together with ductility | Composition, microstructure and heat treatment |
| Example | Glass is hard but not tough | Mild steel is tough | High-tensile steel is strong |

For example, a diamond is very hard but brittle, rubber is tough but not hard, and concrete has high compressive strength but low toughness.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Hardness is resistance to
   A. energy absorption
   B. scratching or indentation of the surface
   C. maximum load per area
   D. cyclic loads
   Answer: B. Hardness is surface resistance. (Key point: Hardness)

2. Toughness is measured by
   A. the Mohs scale
   B. stress in N/mm^2
   C. energy absorbed up to fracture (area under curve)
   D. Brinell hardness
   Answer: C. Impact test or area under curve. (Key point: Toughness)

3. Which pair is correct?
   A. Glass is tough but not hard
   B. Diamond is tough and not hard
   C. Rubber is hard but not tough
   D. Glass is hard but not tough
   Answer: D. Glass is hard but brittle; rubber is tough but not hard. (Key point: Example)

4. Strength is
   A. the maximum stress a material can carry before failure
   B. resistance to scratching
   C. energy to fracture
   D. ability to be hammered
   Answer: A. Strength is stress at failure. (Key point: Strength)

## Related in Civil Engineering Materials

- [Modulus of toughness and resilience (250 kN)](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Anumerical-toughness-resilience-300mm) — Civil Engineering Materials, chapter 1, asked 2×
- [Modulus of toughness and resilience (300 kN)](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Anumerical-toughness-resilience-400mm) — Civil Engineering Materials, chapter 1, asked 2×

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- [Hardness, toughness and aggregate blend](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahardness-toughness-blend) — Transportation Engineering I, chapter 6
- [Hardness versus strength](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Ahardness-versus-strength) — Engineering Geology I, chapter 3
- [Estimation vs testing; CI for hardness](https://www.bctengineer.com/question.md?key=semester_5%2Fprobability_and_statistics%3Aestimation-vs-hypothesis-ci-magnesium) — Probability and Statistics, chapter 6
- [Stress concentration and its effect in brittle material](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Astress-concentration-brittle-effect) — Strength of Materials, chapter 3