Metric Units

1. Units in Part A Numeracy

Metric conversion is an important part of the NMC CBT numeracy assessment, particularly when answering medication calculation questions. As a nurse, you need to confidently convert between units such as grams (g), milligrams (mg), micrograms (mcg), litres (L), and millilitres (mL). Before performing any calculation, always check that the prescribed dose and the available medication are expressed in the same unit.

Remembering simple relationships such as 1 g = 1,000 mg and 1 mg = 1,000 mcg will help you complete calculations accurately and safely. With regular practice, metric conversions can become one of the simplest parts of your CBT numeracy preparation.

Medication calculations, these are the key metric units to recognise and write correctly:

Important CBT tip: Unit symbols are not pluralised. Write 10 mL, not 10 mLs/mls; 500 mg, not 500 mgs; and 2 kg, not 2 kgs.

For calculations, remember: 1 kg = 1,000 g, 1 g = 1,000 mg, 1 mg = 1,000 micrograms, and 1 L = 1,000 mL.

Smaller unit = MULTIPLY × 1,000
Larger unit = DIVIDE ÷ 1,000

So:

g ⟶ mg ⟶ mcg = × 1,000 each step

g ⟵ mg ⟵ mcg = ÷ 1,000 each step

See few examples..

Question 1 – mg → mcg
A patient is prescribed 0.75 mg of a medication. How many micrograms (mcg) is this?

A. 75 mcg
B. 750 mcg
C. 7,500 mcg
D. 0.75 mcg

Answer: B — 750 mcg
Calculation: 0.75 × 1,000 = 750 mcg

Question 2 – mcg → mg
A patient requires 500 mcg of a medication. Convert this dose to milligrams (mg).

A. 0.05 mg
B. 0.5 mg
C. 5 mg
D. 50 mg

Answer: B — 0.5 mg
Calculation: 500 ÷ 1,000 = 0.5 mg

Question 3 – g → mg
The prescription states 1.5 g of a medication. How many milligrams (mg) is this?

A. 150 mg
B. 1,500 mg
C. 15,000 mg
D. 0.15 mg

Answer: B — 1,500 mg
Calculation: 1.5 × 1,000 = 1,500 mg

Question 4 – mg → g
A patient is prescribed 750 mg of a medication. Convert this dose to grams (g).

A. 0.075 g
B. 0.75 g
C. 7.5 g
D. 75 g

Answer: B — 0.75 g
Calculation: 750 ÷ 1,000 = 0.75 g