📏 Inch vs CM: What’s the Difference and How to Convert

Whether you’re measuring for a craft, planning a lesson, or shopping online, you’ve likely seen both inches and centimetres (cm) used. But what exactly is the difference between them?

In this guide, we’ll break down inch vs cm, explain how to convert between them, and share easy tips to help children (and adults!) understand both measurement systems.

📐 What is an Inch?

An inch is a unit of length in the imperial system, which is commonly used in the United States, and in some cases, the UK.

• 1 inch = 2.54 centimetres

• The symbol for inch is “in” or sometimes ″

Inches are often used for:

• Measuring screens (TVs, phones)

• Height (in the US)

• Tools, woodwork, or fabric

📏 What is a Centimetre (cm)?

A centimetre is a unit of length in the metric system, used widely across the world, especially in Europe and scientific communities.

• 1 centimetre = 0.3937 inches

• The symbol for centimetre is cm

Centimetres are used for:

• Measuring height (in most countries)

• Rulers, schoolwork, and science

• Everyday measurements like length of paper, pencil cases, etc.

🔢 Inch vs CM – Quick Comparison Chart

🔄 How to Convert Inches to Centimetres

👉 Formula:

Inches × 2.54 = Centimetres

Example:

• 5 inches × 2.54 = 12.7 cm

👉 Handy Conversion Chart:

🔄 How to Convert Centimetres to Inches

👉 Formula:

Centimetres ÷ 2.54 = Inches

Example:

• 10 cm ÷ 2.54 = 3.93 inches

🧒 Teaching Inches vs CM in Primary Schools

Understanding metric vs imperial is part of the UK primary maths curriculum (KS2), and it’s also a real-life skill. Here’s how to teach the difference:

• Use real rulers showing both inches and cm

• Get children to measure everyday classroom objects in both units

• Introduce story problems: “If your book is 20cm long, how many inches is that?”

• Use visuals like charts, string, or blocks to compare lengths

✏️ Tip: Emphasise that centimetres are part of the metric system (multiples of 10), which makes them easier for calculations.

🌍 Why Do We Have Two Systems?

You might wonder: Why do we use both inches and cm?

• The imperial system is older and traditionally used in the UK and US.

• The metric system is now the global standard, used in science, trade, and education.

• In the UK, you’ll find both systems depending on the context (e.g., centimetres in school, inches for TV sizes).

🧠 Inch vs CM Memory Tips

• “Centi” means hundred in Latin – there are 100 cm in a metre

• “Inch” comes from Latin uncia (a twelfth) – 12 inches in a foot

• 1 inch ≈ 2.5 cm (a quick way to estimate!)

✅ Summary: Inch vs CM

• Inch = Imperial, used mainly in the US

• Centimetre = Metric, used globally

• 1 inch = 2.54 cm, and 1 cm ≈ 0.39 inches

• Learn both – especially useful in school, travel, online shopping, and DIY!

🔗 Helpful Tools and Resources

Here are some trusted websites to help you convert and teach inches vs cm:

• BBC Bitesize: Metric and Imperial Units

• Math is Fun – Length Conversion

• National Physical Laboratory – UK Measurements

• RapidTables – Inches to CM Converter

• Metric Conversion

📥 Want a Free Classroom Conversion Chart?

👉 Download our Inch vs CM Comparison Poster – perfect for KS1/KS2 classrooms and home learning displays.
[Add your link or email opt-in here]

📚 Related Posts:

• Top 10 Outdoor Maths Ideas for KS1

• How to Teach Units of Measure in EYFS

• World Maths Day Activities for Primary Learners

1m Measure Venn Diagram

Measurement KS2

Outdoor Shape, Space & Measure