Imperial and Metric Units (KS2)

ME17Imperial and Metric Units

Miles, pints, inches — the older units still in use.

The UK still uses some imperial units — know the rough metric equivalents.

The conversions worth knowing.

1 mile ≈ 1.6 km

1 inch = 2.5 cm

1 pint ≈ 568 ml

1 kg ≈ 2.2 pounds (lb)

Road signs use miles; milk comes in pints; heights are often given in feet and inches.

Learn the Key Facts

1Length.

1 inch = 2.5 cm · 1 foot = 12 inches ≈ 30 cm · 1 mile ≈ 1.6 km.

5 miles ≈ 8 km

2Mass and capacity.

1 kg ≈ 2.2 lb · 1 pint ≈ 568 ml (about half a litre... a bit more).

1 pint ≈ 568 ml

3Convert with the fact.

8 inches = 8 × 2.5 = 20 cm. 10 miles ≈ 10 × 1.6 = 16 km.

8 in = 20 cm

💡 Key IdeaThe exam gives the conversion fact — your job is to multiply or divide with it correctly.

Worked Example

A road sign says 15 miles to town. Roughly how many kilometres is that? (1 mile ≈ 1.6 km)

Set up

15 × 1.6

→

Calculate

15 × 1.6 = 15 + 9 = 24

(15 × 1) + (15 × 0.6)

→

✓ Answer

≈ 24 km

Watch Out! Common Mistakes

Dividing when you should multiply.

15 miles = 15 ÷ 1.6 = 9.4 km ✕

Sense-check! A mile is LONGER than a km, so 15 miles must be MORE km: 24 km.

Feet and inches muddle.

1 foot = 10 inches ✕

Wrong! 1 foot = 12 inches. (Imperial isn’t base ten — that’s why metric is easier!)

Treating a pint as exactly half a litre.

2 pints = 1000 ml ✕

Close but no. 1 pint ≈ 568 ml, so 2 pints ≈ 1136 ml — more than a litre.

⬇ Cheat Sheet

IMPERIAL AND METRIC UNITS

1 inch = 2.5 cm · 1 foot = 12 inches
1 mile ≈ 1.6 km (so 5 miles ≈ 8 km)
1 pint ≈ 568 ml · 1 kg ≈ 2.2 lb
Sense-check the direction: miles→km gets bigger.

Example: 15 miles × 1.6 ≈ 24 km

📖 Continue Your Journey

✓ ME1 Units of Length ✓ ME2 Converting Length ✓ ME3 Units of Mass ✓ ME4 Converting Mass ✓ ME5 Units of Capacity ✓ ME6 Converting Capacity ✓ ME7 Reading Scales ✓ ME8 Perimeter ✓ ME9 Area of Rectangles ✓ ME10 Area of Triangles ✓ ME11 Area of Parallelograms ✓ ME12 Compound Shapes ✓ ME13 Volume of Cuboids ✓ ME14 Telling the Time ✓ ME15 Time Calculations ✓ ME16 Money Calculations ME17 Imperial and Metric Units ME18 Measurement Problem Solving

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Next Lesson: ME18 Measurement Problem SolvingMixed measurement problems, exam style.

📄 Free printable: Download the Imperial and Metric Units cheat sheet (PDF) — keep it by your child's desk.

Quick summary

Key facts: 1 inch = 2.5 cm, 1 foot = 12 inches, 1 mile ≈ 1.6 km, 1 pint ≈ 568 ml, 1 kg ≈ 2.2 lb.
Exams supply the conversion fact — apply it by multiplying or dividing.
15 miles ≈ 24 km; 8 inches = 20 cm.
Sense-check the direction: miles to km should get bigger.

Frequently asked questions

Which imperial units do children need to know?

Miles (with 1 mile ≈ 1.6 km), inches and feet (1 inch = 2.5 cm, 1 foot = 12 inches), pints (≈ 568 ml) and pounds (1 kg ≈ 2.2 lb) — the units still used on UK roads and in shops.

Do children need to memorise the conversion numbers?

Questions usually provide the fact ('1 mile ≈ 1.6 km'). What's tested is using it correctly — deciding whether to multiply or divide.

Why does the UK mix imperial and metric?

History: metric is standard in science and school, but road signs, milk and body height kept their older units — so both appear in daily life and in exams.

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