Convert Ounces to Kilograms

The Ounce (symbol: oz) is a unit of weight & mass. An imperial unit of mass equal to exactly 1/16 of an avoirdupois pound = 28.349523125 g per NIST SP 811. The avoirdupois ounce is the everyday US small-mass unit for: food portion sizes per FDA 21 CFR 101.9 + USDA Food Patterns (typical protein serving 3 oz cooked meat; 1 oz cheese; 1 oz nuts; 8 oz cup of liquid; lean meat lean 3-4 oz recommended per meal), American cookbook ingredient measurements (1 tablespoon = 0.5 fl oz volume but the 'oz' in 'oz of flour' is mass = 28.35 g), boxing glove weights per Boxing Association rules (typical 8-10 oz pro-boxing; 12-16 oz training-bag), postal rates per USPS (Domestic First-Class up to 13 oz, then Priority Mail rates; international First-Class up to 4 lb in oz increments), and chocolate-bar + nut + cereal-product labeling. Reference values: 1 stick of US butter = 4 oz = 1/2 cup = 8 tablespoons; an Apple iPhone 15 Pro Max ~7.8 oz; a US baseball regulation 5-5¼ oz per MLB rule 3.01. CRITICAL: distinct from troy ounce (~31.103 g, used exclusively for precious metals — 1 troy oz Au differs from 1 avoirdupois oz Au by ~10%, a common confusion when comparing gold quotes to grocery scales). Convert avoirdupois oz to grams by multiplying by 28.349; to troy oz by dividing by 1.097.

It belongs to the imperial measurement system.

Ounces are commonly used in cooking, shipping, fitness, and scientific research.

The Kilogram (symbol: kg) is a unit of weight & mass. The SI base unit of mass per ISO 80000-3 §3-4 and BIPM SI Brochure 9th edition, redefined in 2019 by fixing the Planck constant h = 6.62607015 × 10⁻³⁴ J·s exactly. The kilogram was historically defined (1889-2019) by the International Prototype of the Kilogram (IPK) — a platinum-iridium cylinder at BIPM Pavillon de Breteuil in Sèvres, France — but the 2019 redefinition tied it to a fundamental constant, removing the only remaining artifact-based SI base unit. The kilogram is realized in practice by the Kibble (watt) balance method at NIST, NPL, NIM, NRC Canada, KRISS, and ~12 other national metrology institutes worldwide. Reference values: 1 kg of water at 4°C occupies almost exactly 1 liter (a design feature of the original 1795 metric system); typical newborn human 3.0-3.5 kg; ICE-vehicle dry curb weight 1,200-2,500 kg; commercial aircraft Boeing 737 MTOW 79,000 kg, Airbus A380 575,000 kg; cargo container TEU full load 24,000 kg gross. Kilograms are the global standard for: scientific measurement, shipping weights per IMO + IATA + ICAO, food packaging in most of the world per EU Reg 1169/2011 + Codex Alimentarius, body weight outside the US (clinical BMI calculations require kg per WHO), and bulk industrial trade.

It belongs to the metric measurement system.

Kilograms are commonly used in cooking, shipping, fitness, and scientific research.