Pounds and ounces to kilograms
Birth weights, parcels and recipes from the US and the UK come as pounds plus ounces. Enter the two parts and get kilograms and grams; or type a metric weight to get it back in pounds and ounces.
7 lb 4 oz = 3.288 kg · 8 lb = 3.629 kg · 3.5 kg = 7 lb 11.5 oz
lb + oz → kg
= 3,288.54 g · 116 oz total
kg → lb + oz
How the conversion works
The avoirdupois pound is defined as exactly 0.453 592 37 kg, and it has 16 ounces, so an ounce is exactly 28.349 523 125 g. A weight of P pounds and O ounces is therefore (16 × P + O) × 28.349523125 grams. The reverse divides the grams by 28.349523125, keeps the whole pounds from a division by 16, and reports the remainder in ounces, rounded here to two decimals.
For weights that are only in pounds or only in ounces, the pounds to kg and ounces to grams pages apply directly. Stones and pounds (UK body weight) use 14 pounds to the stone; see stone to kg.
Birth weight chart, 5 lb to 11 lb
In steps of a quarter pound (4 oz), the way maternity units usually round.
| Pounds and ounces | Total ounces | g | kg |
|---|---|---|---|
| 5 lb 0 oz | 80 | 2,268 | 2.26796 |
| 5 lb 4 oz | 84 | 2,381 | 2.38136 |
| 5 lb 8 oz | 88 | 2,495 | 2.49476 |
| 5 lb 12 oz | 92 | 2,608 | 2.60816 |
| 6 lb 0 oz | 96 | 2,722 | 2.72155 |
| 6 lb 4 oz | 100 | 2,835 | 2.83495 |
| 6 lb 8 oz | 104 | 2,948 | 2.94835 |
| 6 lb 12 oz | 108 | 3,062 | 3.06175 |
| 7 lb 0 oz | 112 | 3,175 | 3.17515 |
| 7 lb 4 oz | 116 | 3,289 | 3.28854 |
| 7 lb 8 oz | 120 | 3,402 | 3.40194 |
| 7 lb 12 oz | 124 | 3,515 | 3.51534 |
| 8 lb 0 oz | 128 | 3,629 | 3.62874 |
| 8 lb 4 oz | 132 | 3,742 | 3.74214 |
| 8 lb 8 oz | 136 | 3,856 | 3.85554 |
| 8 lb 12 oz | 140 | 3,969 | 3.96893 |
| 9 lb 0 oz | 144 | 4,082 | 4.08233 |
| 9 lb 4 oz | 148 | 4,196 | 4.19573 |
| 9 lb 8 oz | 152 | 4,309 | 4.30913 |
| 9 lb 12 oz | 156 | 4,423 | 4.42253 |
| 10 lb 0 oz | 160 | 4,536 | 4.53592 |
| 10 lb 4 oz | 164 | 4,649 | 4.64932 |
| 10 lb 8 oz | 168 | 4,763 | 4.76272 |
| 10 lb 12 oz | 172 | 4,876 | 4.87612 |
| 11 lb 0 oz | 176 | 4,990 | 4.98952 |
Common mistakes
Writing 7.4 lb for 7 lb 4 oz is the most frequent error: 7.4 lb is 7 pounds and 6.4 ounces (3.357 kg), not 3.288 kg. Ounces are sixteenths of a pound, so 4 oz is 0.25 lb and 8 oz is 0.5 lb. The other trap is the fluid ounce, a volume of 29.57 mL that happens to weigh about 29.6 g for water and something else for everything else; recipe conversions by ingredient are on the cooking pages.
Frequently asked questions
7 lb 4 oz is 116 ounces; 116 × 28.349523125 g = 3,288.5 g, that is 3.29 kg.
Multiply the pounds by 16, add the ounces, multiply the total ounces by 28.349523125 to get grams, and divide by 1,000 for kilograms. Or convert the pounds (× 0.45359237 kg) and the ounces (× 0.028349523 kg) separately and add them.
Divide the kilograms by 0.45359237 to get decimal pounds, keep the whole pounds, and multiply the fraction by 16 for the ounces. 3.5 kg = 7.716 lb = 7 lb 11.5 oz, usually rounded to 7 lb 12 oz.
The avoirdupois pound used for people, food and parcels is 16 ounces. The troy pound of 12 ounces is used only for precious metals, and the fluid ounce is a volume, not a weight.
Most full-term babies weigh between 2.5 kg and 4.5 kg (5 lb 8 oz to 9 lb 15 oz). Hospitals in the US, the UK and Ireland often report the figure in pounds and ounces, hence the chart above.