Hospitals record newborns in grams, airlines cap bags in kilograms, international recipes and shipping labels expect metric — yet a US scale reads in pounds. This converter turns pounds into kilograms exactly, and it accepts pounds and ounces together so a reading like 7 lb 8 oz never needs to be turned into a decimal by hand.
How to use the pounds to kg converter
- Enter the whole pounds in Pounds (lb). Decimal pounds such as 152.6 also work.
- If the reading includes ounces, type them in Plus ounces (optional).
- The result shows kilograms, plus grams and stone-and-pounds. Below are a pounds-to-kilograms chart and a birth-weight table in half-pound steps.
Pounds to kilograms formula
With ounces, convert to ounces first. An avoirdupois ounce is exactly 1/16 lb, or 28.349523125 g:
Worked example: a newborn’s birth weight
Step 1. 7 lb 8 oz in ounces: 7 × 16 + 8 = 120 oz.
Step 2. 120 × 0.028349523125 = 3.4019 kg, or 3,402 g.
Check. 7.5 lb × 0.45359237 gives the same 3.4019 kg.
A second example: an adult who weighs 150 lb is 150 × 0.45359237 = 68.0389 kg.
Birth weights in pounds, ounces and grams
Birth announcements in the US quote pounds and ounces, while hospital records and growth charts worldwide use grams. A few reference points:
| Birth weight | Kilograms | Grams |
|---|---|---|
| 5 lb 8 oz | 2.495 | 2,495 |
| 6 lb 0 oz | 2.722 | 2,722 |
| 7 lb 0 oz | 3.175 | 3,175 |
| 7 lb 8 oz | 3.402 | 3,402 |
| 8 lb 0 oz | 3.629 | 3,629 |
| 9 lb 0 oz | 4.082 | 4,082 |
Clinicians commonly use 2,500 g — about 5 lb 8 oz — as the threshold for low birth weight. The calculator’s own table extends this from 5 lb to 10 lb in 8-ounce steps.
This converter is for unit conversion only. Medicine doses calculated per kilogram of body weight should always come from a pharmacist or clinician, using the weight they measure.
Luggage limits
| Limit as written | Pounds | Kilograms |
|---|---|---|
| Common US checked-bag limit | 50 | 22.68 |
| Common international limit | 50.71 | 23 |
| Heavy-bag limit | 70 | 31.75 |
The pound limits and kilogram limits are designed to match, but they are not identical. A bag at 50.5 lb passes a 23 kg check and fails a 50 lb one.
US gym plates in kilograms
| Plate or bar | Pounds | Kilograms |
|---|---|---|
| Small plate | 2.5 | 1.13 |
| Plate | 5 | 2.27 |
| Plate | 10 | 4.54 |
| Plate | 25 | 11.34 |
| Plate | 35 | 15.88 |
| Plate or standard bar | 45 | 20.41 |
A 45 lb bar is 0.41 kg heavier than a 20 kg competition bar, so lifters switching between systems see slightly different totals for the “same” setup. To go the other way, use the kg to lbs converter; for UK body weights, the stone to kg converter takes stones and pounds directly.
Frequently asked questions
How many kilograms are in a pound?
Exactly 0.45359237 kg. The pound has been defined this way since 1959, so multiplying by 0.45359237 is an exact conversion.
How do I convert pounds and ounces to kg?
Convert everything to ounces (pounds × 16 + ounces), then multiply by 0.028349523125. For a baby weighing 7 lb 8 oz: 7 × 16 + 8 = 120 oz, and 120 × 0.028349523125 = 3.4019 kg, or about 3,402 g.
What is 150 lbs in kg?
150 lb is 68.0389 kg, which most people round to 68 kg.
Is a 50 lb bag allowed under a 23 kg baggage limit?
Yes, just. 50 lb is 22.68 kg, while 23 kg is 50.71 lb. With so little margin, weigh the packed bag rather than estimating.
What is the quickest mental conversion from lb to kg?
Halve the pounds, then subtract 10% of that half. For 150 lb: 75 − 7.5 = 67.5 kg, against an exact 68.04. The shortcut runs about 0.8% low.