Pounds and Ounces Calculator
Add or subtract weights in pounds and ounces, turn decimal pounds into lb and oz, and convert kilograms or grams to pounds and ounces.
Total oz = lb × 16 + oz · 1 oz = 28.349523125 g
Decimal Pounds Are Not Pounds and Ounces
Deli scales, shipping scales and spreadsheets usually show decimal pounds, while recipes, baby records and package labels use pounds and ounces. 2.35 lb is not 2 lb 35 oz or 2 lb 3.5 oz. The decimal part is a fraction of a 16-ounce pound, so multiply it by 16: 0.35 × 16 = 5.6, giving 2 lb 5.6 oz.
| Decimal lb | Ounces |
|---|---|
| 0.1 lb | 1.6 oz |
| 0.2 lb | 3.2 oz |
| 0.25 lb | 4 oz |
| 0.3 lb | 4.8 oz |
| 0.4 lb | 6.4 oz |
| 0.5 lb | 8 oz |
| 0.6 lb | 9.6 oz |
| 0.7 lb | 11.2 oz |
| 0.75 lb | 12 oz |
| 0.8 lb | 12.8 oz |
| 0.9 lb | 14.4 oz |
| Ounces | Decimal lb |
|---|---|
| 1 oz | 0.0625 |
| 2 oz | 0.125 |
| 3 oz | 0.1875 |
| 4 oz | 0.25 |
| 6 oz | 0.375 |
| 8 oz | 0.5 |
| 10 oz | 0.625 |
| 12 oz | 0.75 |
| 14 oz | 0.875 |
| 15 oz | 0.9375 |
Worked Example: A Newborn’s Weight Change
A baby is born at 7 lb 8 oz and weighs 6 lb 15 oz at the day-3 check. How much is that, and what share of birth weight? (This is the calculator's Load Example.)
Step 1: Convert both weights to ounces
Step 2: Subtract
Step 3: As a percentage of birth weight
The baby is down 9 oz, or 7.5%. In metric that's 3.40 kg to 3.15 kg. Working in ounces avoids the borrowing mistakes that come from subtracting 8 − 15 directly.
Newborns usually lose some weight in the first days and are back to birth weight by about two weeks. Whether a particular loss is a concern is for your pediatrician or midwife to judge, not a calculator.
Birth Weights in kg and lb oz
Hospitals in most countries weigh babies in grams, but family often asks in pounds and ounces. The WHO defines low birth weight as under 2,500 g, which is just over 5 lb 8 oz.
| Kilograms | Grams | Pounds and ounces |
|---|---|---|
| 2.5 kg | 2,500 | 5 lb 8.2 oz |
| 3 kg | 3,000 | 6 lb 9.8 oz |
| 3.5 kg | 3,500 | 7 lb 11.5 oz |
| 4 kg | 4,000 | 8 lb 13.1 oz |
| 4.5 kg | 4,500 | 9 lb 14.7 oz |
Adding Up a Parcel for Postage
You're pricing a parcel before you have a scale big enough: the boxed item weighs 1 lb 6 oz, the packing material 5 oz and a second item 12.4 oz.
39.4 ÷ 16 = 2 remainder 7.4 → 2 lb 7.4 oz (1.12 kg)
Carriers round any fraction up, so this parcel is charged as 3 lb. Under a pound, USPS prices Ground Advantage in ounce steps instead, which is why the calculator shows both the nearest ounce and the rounded-up weight.
Carrying and Borrowing by Hand
Pounds and ounces work like hours and minutes: you carry and borrow in sixteens, not tens.
- Adding: 3 lb 11 oz + 2 lb 9 oz = 5 lb 20 oz. 20 oz is 1 lb 4 oz, so the answer is 6 lb 4 oz.
- Subtracting: 5 lb 3 oz − 2 lb 9 oz. You can't take 9 from 3, so borrow a pound: 4 lb 19 oz − 2 lb 9 oz = 2 lb 10 oz.
- Multiplying: 4 bags of 1 lb 12 oz = 4 lb 48 oz = 4 lb + 3 lb = 7 lb.
If that feels error-prone, convert everything to ounces first, do the sum, then divide by 16 at the end. That's exactly what the calculator does.
Frequently asked questions
Is 1.5 lb the same as 1 lb 5 oz?
No. 1.5 lb is one and a half pounds, which is 1 lb 8 oz. 1 lb 5 oz is 1.3125 lb.
My scale shows 1:08. What does that mean?
Many kitchen and baby scales show pounds and ounces separated by a colon, so 1:08 means 1 lb 8 oz, not 1.08 lb. Check whether your scale is set to lb:oz or decimal pounds before writing the reading down.
Are these weight ounces or fluid ounces?
Weight (avoirdupois) ounces, 16 to the pound. Fluid ounces measure volume. A fluid ounce of water happens to weigh about 1 oz, but most other liquids don't.
Can I enter weights like 0 lb 40 oz?
Yes. Any number of ounces is accepted, and anything over 16 carries into pounds, so 40 oz shows as 2 lb 8 oz.
Sources
- NIST Handbook 44, Appendix C: avoirdupois ounce = 1/16 lb = 28.349523125 g.
- World Health Organization: low birth weight: defined as a birth weight under 2,500 g.
- American Academy of Pediatrics (HealthyChildren.org): newborn weight loss and regaining birth weight.
- USPS Notice 123 price list: ounce price steps under 1 lb and whole-pound pricing above.
Related Tools
Convert decagrams to grams.
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Convert grams to ounces.
Convert kilograms to pounds.
Convert micrograms (mcg) to milligrams (mg).
Convert pounds to kilograms.