📋 Health Information · Editorial Team
Baby Weight in Stone: UK Chart
The average UK newborn weighs 3.4 kg (7 lb 8 oz). Convert any baby weight between kg, pounds, ounces and stone with the chart below.
Note for parents: This chart is for unit conversion only. Your baby's growth is tracked on percentile charts in the UK red book (personal child health record). If you are concerned about your baby's weight or feeding, speak to your health visitor or GP.
Do Parents Use Stone for Babies?
Honestly, no. A stone is 14 pounds, and most newborns weigh well under 10 pounds, so stone is too large a unit to be useful. In the UK, baby weights are given in pounds and ounces ("7 lb 8 oz") or in kilograms in medical settings. The red book records birth weight in both.
That said, many parents search for baby weights "in stone" out of habit, since stone is how the family talks about adult weight. The chart below gives every common birth weight in all four units so nothing is lost in translation.
Newborn Weight Conversion Chart
| Kilograms | Pounds & Ounces | Stone Equivalent | Note |
|---|---|---|---|
| 2.5 kg | 5 lb 8 oz | 0 st 5.5 lb | Low birth weight threshold |
| 2.7 kg | 5 lb 15 oz | 0 st 6.0 lb | |
| 3.0 kg | 6 lb 10 oz | 0 st 6.6 lb | |
| 3.2 kg | 7 lb 1 oz | 0 st 7.1 lb | |
| 3.4 kg | 7 lb 8 oz | 0 st 7.5 lb | UK average |
| 3.6 kg | 7 lb 15 oz | 0 st 7.9 lb | |
| 3.8 kg | 8 lb 6 oz | 0 st 8.4 lb | |
| 4.0 kg | 8 lb 13 oz | 0 st 8.8 lb | Upper normal range |
| 4.2 kg | 9 lb 4 oz | 0 st 9.3 lb | |
| 4.5 kg | 9 lb 15 oz | 0 st 9.9 lb | Large baby |
The NHS defines normal birth weight as 2.5 kg to 4.0 kg. Babies below 2.5 kg are classed as low birth weight.
Baby Growth Milestones (Average)
These are rough averages. Healthy babies vary enormously, and your health visitor tracks your baby against percentile curves, not fixed targets.
| Age | Average Weight | In lb & oz |
|---|---|---|
| Birth | 3.4 kg | 7 lb 8 oz |
| 3 months | 6.0 kg | 13 lb 4 oz |
| 6 months | 7.5 kg | 16 lb 8 oz |
| 9 months | 8.8 kg | 19 lb 6 oz |
| 12 months | 9.6 kg | 21 lb 3 oz |
Babies typically lose up to 10 percent of birth weight in the first days, then regain it by 2 to 3 weeks. They roughly double birth weight by 5 to 6 months and triple it by 12 months.
Frequently Asked Questions
How much does a newborn baby weigh in stone?
The average UK newborn weighs about 3.4 kg, which is 7 lb 8 oz. In stone that is 0 stone 7.5 pounds, usually just said as 7 lb 8 oz. Babies are weighed in pounds and ounces, not stone.
What is a healthy birth weight in the UK?
The NHS considers 2.5 kg to 4.0 kg (5 lb 8 oz to 8 lb 13 oz) a normal birth weight range. The average is around 3.4 kg (7 lb 8 oz).
How do I convert my baby's weight from kg to stone?
Divide the kg by 6.35029 to get stone. For example, 4 kg is 0.63 stone, but in practice UK parents and health visitors say pounds and ounces: 4 kg is 8 lb 13 oz.
Why are babies weighed in lb and oz instead of stone?
A stone (14 lb) is too large a unit for babies. Most newborns weigh under 10 lb, so pounds and ounces give the precision needed to track growth. The UK red book records birth weight in kg and lb/oz.
How much should a baby weigh at 6 months?
On average, babies roughly double their birth weight by 5 to 6 months. A 3.4 kg newborn would typically weigh around 7 to 7.5 kg (15 lb 7 oz to 16 lb 8 oz) at 6 months, though healthy ranges vary widely.