Pounds and Ounces Calculator
Add and convert pounds and ounces. Enter whole pounds and ounces (ounces can exceed 16 — they carry automatically) to get decimal pounds, total ounces, a normalized lb and oz weight, and kilograms with grams.
Example: with Pounds 7 · Ounces 8 → Decimal pounds: 7.5 lb.
- Total ounces120 oz
- Pounds and ounces7 lb 8 oz
- In metric3.4 kg (3,402 g)
Computed by the calculator below using its default values. Change any input to see your own numbers.
decimal lb = lb + oz ÷ 16. A pound is 16 ounces, so 7 lb 8 oz is 7.5 lb — not 7.8.
Base 16, not base 10
Pounds and ounces are a base-16 system: 16 ounces to the pound. That is why 7 lb 8 oz is 7.5 decimal pounds — the 8 ounces are half a pound, not eight tenths. Postal scales, shipping labels, and produce scales usually display decimal pounds, while birth weights and boxing weigh-ins stay in pounds and ounces, so translating between the two formats is a daily chore.
The conversion runs both directions here. Decimal pounds come from lb + oz ÷ 16; total ounces from lb × 16 + oz. If you enter more than 16 ounces, the calculator carries them into pounds the way you would carry digits in addition — 6 lb 20 oz normalizes to 7 lb 4 oz. Metric weight uses the exact definition of 453.59237 grams per pound.
How it’s calculated
Total ounces = pounds × 16 + ounces; decimal pounds = total ounces ÷ 16; normalized form shows whole pounds with the remainder rounded to 0.1 oz. Grams = total ounces × 28.349523125 (exact, since 1 lb = 453.59237 g).
Weight (avoirdupois) ounces only — fluid ounces on beverage labels are volume and do not belong in this arithmetic.
Pounds and ounces to decimal and metric
| Pounds & ounces | Decimal pounds | Grams |
|---|---|---|
| 5 lb 8 oz | 5.5 lb | 2,495 g |
| 6 lb 12 oz | 6.75 lb | 3,062 g |
| 7 lb 0 oz | 7 lb | 3,175 g |
| 7 lb 8 oz | 7.5 lb | 3,402 g |
| 8 lb 4 oz | 8.25 lb | 3,742 g |
| 9 lb 0 oz | 9 lb | 4,082 g |
Computed with 1 lb = 16 oz = 453.59237 g (NIST exact); grams rounded to the nearest gram.
Common mistakes
- Typing 7 lb 8 oz as 7.8 lb — that is actually 7 lb 12.8 oz, a third of a pound heavier.
- Reading a postal scale's 7.25 lb as 7 lb 25 oz instead of 7 lb 4 oz.
- Adding two lb-oz weights without carrying: 3 lb 10 oz plus 2 lb 9 oz is 6 lb 3 oz, not 5 lb 19 oz.
- Mixing fluid ounces of formula or milk into a weight calculation.
Frequently asked questions
How do I convert pounds and ounces to decimal pounds?
Divide the ounces by 16 and add to the pounds: decimal lb = lb + oz ÷ 16. For 7 lb 8 oz, that is 7 + 8/16 = 7.5 lb.
Why is 7 lb 8 oz not 7.8 pounds?
Because a pound has 16 ounces, not 10. Eight ounces is 8/16 = 0.5 lb, so 7 lb 8 oz is 7.5 lb. Treating ounces as decimal digits overstates the weight.
How much is 7 lb 8 oz in kilograms?
About 3.4 kg (3,402 g). Multiply decimal pounds by 0.45359237: 7.5 × 0.45359237 = 3.402 kg. Hospitals often chart both formats for newborns.
What happens if I enter more than 16 ounces?
The calculator carries them into pounds automatically. For example, 0 lb 24 oz becomes 1 lb 8 oz, and the decimal result shows 1.5 lb either way.