Pythagoras' Theorem in 3D for GCSE Maths (with Examples and Questions)

Pythagoras’ Theorem extends beyond 2D shapes and is an important concept in GCSE maths for finding diagonal lengths in 3D objects.

At GCSE level, you'll use the formula a² + b² = c² to calculate the longest diagonals and other hidden lengths in 3D shapes such as cuboids, prisms, and pyramids. Understanding Pythagoras in 3D helps solve more complex geometry problems that appear in both exams and real-life applications.

This page focuses on Pythagoras in 3D, with step-by-step explanations and practice questions to build your confidence.

Before learning about how to apply the theorem to 3D problems, make sure you know the basics of Pythagoras' Theorem first.

GCSE Pythagoras in 3D

This video covers everything you need to know about applying Pythagoras’ Theorem in 3D shapes, from basic concepts to exam-style questions.

The rest of the lesson on 3D Pythagoras is not quite ready, but if you already know what you're doing, we have practice questions linked below.