Units of measurement
We measure different things using different units. In the UK, we mainly use metric units (metres, kilograms, litres) but you may also see imperial units (miles, pounds, pints) in everyday life.
Length
mm, cm, m, km / inches, feet, miles
Weight
g, kg / ounces, pounds
Capacity
ml, litres / pints, gallons
Time
seconds, minutes, hours, days
💡 Key conversions: 10 mm = 1 cm · 100 cm = 1 m · 1000 m = 1 km · 1000 g = 1 kg · 1000 ml = 1 litre
Telling the time
Time can be written in 12-hour (am/pm) or 24-hour format. Timetables and digital clocks often use 24-hour time.
60 sec
= 1 minute
60 min
= 1 hour
24 hrs
= 1 day
2:30 pm
= 14:30
💡 24-hour tip: For afternoon times, add 12 to the hour. 3 pm = 15:00. 9 pm = 21:00. Midnight = 00:00. Noon = 12:00.
2D Shapes
Flat shapes (2D) have length and width but no depth. Here are the key ones you need to know at Entry Level:
Square
4 equal sides, 4 right angles
Rectangle
2 pairs of equal sides, 4 right angles
Triangle
3 sides, 3 angles
Circle
Perfectly round, no corners
Perimeter & Area
Perimeter is the total distance around the outside of a shape — add up all the sides.
Area is how much space a shape covers. For rectangles: Area = length × width.
Perimeter
Sum of all sides (cm, m)
Area
Length × Width (cm², m²)
5 × 3 = 15
Area of a 5m × 3m room
💡 Remember: Area is always measured in square units (cm² or m²). Perimeter is measured in regular units (cm or m).
1Converting units of length
▼
A piece of ribbon is 2.5 metres long. How long is this in centimetres?
- 1There are 100 cm in 1 metre.
- 2Multiply: 2.5 × 100 = 250 cm
✅ Answer: 250 cm
2Reading the time — 24-hour clock
▼
A train leaves at 14:35 and arrives at 16:10. How long is the journey?
- 1From 14:35 to 15:00 = 25 minutes
- 2From 15:00 to 16:10 = 1 hour 10 minutes
- 3Total: 25 min + 1 hr 10 min = 1 hour 35 minutes
✅ Answer: The journey is 1 hour 35 minutes.
3Calculating perimeter
▼
A rectangular garden is 8 m long and 5 m wide. What is the perimeter?
- 1Perimeter = add all sides. A rectangle has 2 long sides and 2 short sides.
- 28 + 8 + 5 + 5 = 26 m
- 3Or use the formula: 2 × (8 + 5) = 2 × 13 = 26 m
✅ Answer: The perimeter is 26 m.
4Calculating area
▼
A bedroom floor is 4 m long and 3.5 m wide. What is the area?
- 1Area of a rectangle = length × width
- 24 × 3.5 = 14 m²
✅ Answer: The area is 14 m².
5Converting weight
▼
A bag of potatoes weighs 2.5 kg. How much is this in grams?
- 1There are 1000 g in 1 kg.
- 2Multiply: 2.5 × 1000 = 2500 g
✅ Answer: 2500 g
6Reading a scale
▼
A ruler shows markings at 0, 5, 10 and 15 cm. A pencil ends halfway between 10 and 15. How long is the pencil?
- 1Find the midpoint between 10 and 15: (10 + 15) ÷ 2 = 12.5
- 2The pencil ends at 12.5 cm.
✅ Answer: The pencil is 12.5 cm long.
Question 1
How many centimetres are in 3.2 metres?
Question 2
A bus leaves at 09:15 and the journey takes 45 minutes. When does it arrive?
Question 3
A square has sides of 6 cm. What is its perimeter?
Question 4
A room is 5 m long and 4 m wide. What is the area of the floor?
Question 5
How many grams are in 1.75 kg?
Question 6
What is 3:45 pm in 24-hour clock?
Question 7
How many sides does a hexagon have?
Question 8
A rectangle is 9 cm long and 4 cm wide. What is its area?