BNF for Children (BNFC) 2018-2019

Approximate Conversions and Units

Conversion of pounds to kilograms

lb kg

10. 45

20. 91

31. 36

41. 81

52. 27

62. 72

73. 18

83. 63

94. 08

10 4. 54

11 4. 99

12 5. 44

13 5. 90

14 6. 35

Conversion of stones to kilograms

stones kg

16. 35

212. 70

319. 05

425. 40

531. 75

638. 10

744. 45

850. 80

957. 15

10 63. 50

11 69. 85

12 76. 20

13 82. 55

14 88. 90

15 95. 25

Conversion from millilitres to fluid ounces

mL fl oz

50 1. 8

100 3. 5

150 5. 3

200 7. 0

500 17. 6

1000 35. 2

Length

1 metre (m) = 1000 millimetres (mm)

1 centimetre (cm) = 10 mm
1 inch (in) = 25.4 mm
1 foot (ft) = 12 inches
12 inches = 304.8 mm

Mass

1 kilogram (kg) = 1000 grams (g)

1 gram (g) = 1000 milligrams (mg)

1 milligram (mg) = 1000 micrograms

1 microgram = 1000 nanograms

1 nanogram = 1000 picograms

Volume

1 litre = 1000 millilitres (mL)

1 millilitre (1 mL) = 1000 microlitres

1 pint≈568 mL

Other units

1 kilocalorie (kcal) = 4186.8 joules (J)

1000 kilocalories (kcal) = 4.1868 megajoules (MJ)

1 megajoule (MJ) = 238.8 kilocalories (kcal)

1 millimetre of mercury (mmHg) = 133.3 pascals (Pa)

1 kilopascal (kPa) = 7.5 mmHg (pressure)

Plasma-drug concentrations

Plasma-drug concentrations in BNF publications are

expressed in mass units per litre (e.g. mg/litre). The

approximate equivalent in terms of amount of substance

units (e.g. micromol/litre) is given in brackets.

Prescribing for children: weight, height,

and gender

The table below shows themean valuesfor weight, height

and gender by age; these values have been derived from the

UK-WHO growth charts 2009 and UK 1990 standard centile

charts, by extrapolating the 50 th centile, and may be used to

calculate doses in the absence of actual measurements.

However, the child’s actual weight and height might vary

considerably from the values in the table and it is important

to see the child to ensure that the value chosen is

appropriate. In most cases the child’s actual measurement

should be obtained as soon as possible and the dose re-

calculated.

Age Weight (kg) Height (cm)

Full-term neonate 3. 551

1 month 4. 355

2 months 5. 458

3 months 6. 161

4 months 6. 763

6 months 7. 667

1 year 975

3 years 14 96

5 years 18 109

7 years 23 122

10 years 32 138

12 years 39 149

14 year old boy 49 163

14 year old girl 50 159

Adult male 68 176

Adult female 58 164