Article — Pounds to Ounces Converter
Pounds to ounces: when you start with the pound
One pound equals 16 ounces. To convert pounds to ounces, multiply by 16. 5 lb = 80 oz. 10 lb = 160 oz. The 16 is exact, set by the definition of the avoirdupois pound, with no measurement involved. The relationship runs both ways: divide ounces by 16 to get pounds. This page is for everyone starting with pounds - the cook holding a recipe in pounds, the parent reading a hospital chart, the seller pricing a parcel.
The calculator at the top of the page handles both directions and accepts mixed input like "5 lb 8 oz." Below: how the pound-to-ounce math shows up in cooking, baby weight, and parcel shipping, plus the precious-metals exception that matters if you ever buy gold.
The pounds-to-ounces formula
Multiply pounds by 16. That is the whole formula:
oz = lb x 16 (exact)lb = oz / 16 (exact)(lb x 16) + oz = total ouncesThe relationship has been fixed by definition since the International Yard and Pound Agreement of 1959. One avoirdupois pound is exactly 453.59237 g, and one avoirdupois ounce is exactly 28.349523125 g - one-sixteenth of the pound. No rounding inside the system. Rounding only enters when you cross into metric, and even then only because the numbers have more decimal places than most people need.
Cooking: pounds to ounces in the kitchen
US recipes mix pounds and ounces depending on the scale of the ingredient. A pound of butter or a pound of ground beef shows up as "1 lb" on the package; smaller amounts of the same ingredient appear in ounces. Two sticks of US butter weigh exactly 8 oz, or half a pound, and the wrapper of every standard butter stick prints the equivalence:
- 1 stick US butter = 4 oz = 1/4 lb = 113 g
- 2 sticks (1 cup) butter = 8 oz = 1/2 lb = 227 g
- 1 lb ground beef = 16 oz = 4 quarter-pound patties
- 1 lb pasta = 16 oz, standard US dry pasta box
- 2 lb bag of sugar = 32 oz = 907 g
- 5 lb bag of flour = 80 oz = 2.27 kg
The "Quarter Pounder" hamburger at McDonald's is named for the raw patty weight: a quarter of a pound, or 4 ounces, or 113 g. After cooking, the patty loses about 25% of its weight to moisture and ends up closer to 85 g. The name refers to the patty before grilling. In France, the metric Quarter Pounder is sold as a "Royal" because "quarter pound" does not translate naturally into a metric country.
Baby weight: why hospitals use lb-oz
US hospitals report newborn weight in pounds-plus-loose-ounces - "7 lb 5 oz" - rather than decimal pounds or grams. The convention is over 100 years old, inherited from 19th-century apothecary practice when both patient weights and drug doses were standardised in lb-oz format. The CDC reports average US birth weight at about 7 lb 3 oz (3,260 g) and defines low birth weight as anything below 5 lb 8 oz (2,495 g).
The format matters for clinical decisions. Pediatric drug dosing in the US is still calculated from weight in pounds, and dosage charts use lb-oz directly. A child weighing 17 lb 8 oz gets a different dose from one at 17 lb 0 oz, and conversion errors at the bedside have been a documented source of medication mistakes. The recommendation from the American Academy of Pediatrics, since the early 2000s, has been to record weights in grams or kilograms in addition to lb-oz, precisely to avoid the mixed-format conversion problem.
To go from "7 lb 5 oz" to total ounces, multiply the pounds by 16 and add the loose ounces. (7 x 16) + 5 = 117 oz. To go to kilograms, multiply that by 28.35 then divide by 1000: 117 x 28.35 / 1000 = 3.32 kg. Going via total ounces avoids the "is 5 oz really 0.3 lb?" mental trap.
Parcel rates: USPS, FedEx, UPS
The major US carriers all price parcels in pounds-and-ounces tiers. USPS First-Class Mail handles items up to 13 oz; above that, packages move to Priority Mail, which caps at 70 lb (1,120 oz). FedEx Ground and UPS Ground both allow up to 150 lb per package, but their rate tables jump at every pound up to that limit. For a 5 lb 8 oz package, USPS rounds up to the next pound tier; FedEx and UPS use dimensional weight in addition to actual weight.
The 70 lb cap on USPS Priority is not arbitrary. It comes from a 1970s occupational safety guideline about the maximum weight a postal worker should regularly lift. The metric equivalent (31.75 kg) is heavier than the 23 kg cap most international airlines use for checked baggage.
The mixed-format math trap
The biggest single source of error in pounds-to-ounces math is the mixed format. "5 lb 8 oz" is not 5.8 lb. The loose ounce portion has to be divided by 16 before it can be added to the whole pounds. 8 / 16 = 0.5, so 5 lb 8 oz = 5.5 lb.
The same trap shows up with "3 lb 12 oz" (= 3.75 lb, not 3.12 lb) and "10 lb 4 oz" (= 10.25 lb, not 10.4 lb). The fix is simple: always think of the pound as having 16 ounces, not 10. Pounds-and-ounces is a base-16 mixed system, not a decimal one.
Pounds for gold are different
The 16-ounce pound applies to everything in the US except precious metals. Gold, silver, and platinum are priced and weighed in troy units. A troy pound has only 12 troy ounces, and a troy ounce is heavier than a regular avoirdupois ounce (31.10 g vs 28.35 g - 9.7% heavier).
Weigh gold on a kitchen scale (avoirdupois) and price it at the troy spot price, and you understate the value by 9.7%. On 10 ounces of gold worth roughly $20,000, that is a $2,000 error. Always confirm the ounce type before pricing a precious-metal sale. A jeweller pricing 1 oz of gold at $2,000 means 1 troy ounce; the same gram weight in avoirdupois would price differently.
Common pounds-to-ounces mistakes
Treating "5 lb 8 oz" as 5.8 lb. The 8 oz is half a pound, not eight-tenths. 5 lb 8 oz = 5.5 lb in decimal pounds, or 88 oz in total ounces.
Confusing dry ounces with fluid ounces. A "16 oz" pint of olive oil weighs less than a pound (oil is less dense than water). A "16 oz" pint of honey weighs more than a pound. Fluid ounces measure volume; the 1 lb = 16 oz math applies only to mass.
Using troy ounces for groceries (or avoirdupois for gold). Avoirdupois (16 oz/lb) for everything except precious metals. Troy (12 oz/lb) only for gold, silver, platinum, palladium.
Multiplying by 10 instead of 16. Easy to do when typing fast. Always double-check: a pound has 16 ounces, never 10. The number 16 was chosen specifically because it divides cleanly by 2 down to 1 (16 to 8 to 4 to 2 to 1), making it useful for balance-scale weighing in the medieval wool trade.