Weight Converter — Convert Between All Weight & Mass Units

A weight converter translates between the full spectrum of mass and weight measurement units — from micrograms and milligrams used in pharmacy and nutrition, through grams and kilograms for everyday use, to metric tons and short tons for industrial applications, including the full range of imperial units (ounces, pounds, stones) and specialized units like the troy ounce used in precious metals trading. Enter any weight in any unit and instantly see the equivalent in any other unit with precision across all scales.

Weight measurement systems evolved independently across civilizations and were standardized only recently — and incompletely. The metric system's kilogram, based on the physical properties of water and now defined through fundamental physical constants, coexists with the 2,000-year-old Roman pound, the medieval British stone, the ancient troy ounce of alchemists and goldsmiths, and the avoirdupois ounce of everyday commerce. Each system persists because specific industries and cultures built their practices around it. Pharmaceutical dosing uses milligrams; grocery shopping in the U.S. uses ounces and pounds; body weight in the UK is discussed in stones; commodity trading uses metric tons; gold and silver are priced in troy ounces.

The need to convert between these systems is not diminishing — if anything, global commerce and digital shopping have increased the frequency of weight conversions. A U.S. consumer buying imported food sees gram labels; an investor reading gold market news deals in troy ounces; a person monitoring their health may track body weight in kilograms (as medical professionals require) while thinking in pounds from daily habit. This converter handles all these conversions with exact or high-precision factors.

Example 1 — Body weight conversion: 75 kilograms to pounds: 75 × 2.20462 = 165.35 pounds In stones: 165.35 / 14 = 11.81 stone = 11 stone 11.4 pounds

Example 2 — Gold price calculation: Gold at $1,950 per troy ounce. 1 troy ounce = 31.1035 grams. $1,950 / 31.1035 = $62.70 per gram. 100 grams of gold = 100 × $62.70 = $6,270. 1 kilogram gold = $62,700.

Example 3 — Pharmaceutical dose: Medication dosed at 10 mg/kg for a 68 kg patient. Dose = 10 × 68 = 680 mg = 0.68 grams. If tablet is 200 mg: 680/200 = 3.4 tablets (take 3.5 tablets or adjust to nearest half-tablet).

Example 4 — Shipping weight: Package: 3.2 kg In pounds: 3.2 × 2.20462 = 7.05 pounds In ounces: 7.05 × 16 = 112.8 ounces For U.S. postal shipping: 7.05 pounds (rounds to next pound = 8 lb for postal rate).

Weight conversion errors in medicine and pharmacy have historically caused serious harm. The classic pediatric dosing error involves confusion between pounds and kilograms: a child's weight recorded in pounds (60 lbs) interpreted as kilograms gives a dose 2.2× too high. A 2009 Joint Commission Sentinel Event Alert cited weight-based dosing errors as a significant patient safety risk, specifically highlighting kg/lb confusion as a root cause in overdose incidents. Healthcare settings now require body weight to be recorded in kilograms exclusively, specifically to eliminate this conversion error — but transitions between systems still create risk at system boundaries.

In international trade and commodity markets, weight unit confusion has significant financial consequences. When oil contracts specified in metric tons are processed by software expecting short tons, the apparent volume is 10% different — a difference of hundreds of thousands of dollars per tanker load at scale. Agricultural commodity contracts (grain, soybeans, cotton) are denominated in metric tons on international markets and in short tons or bushels on U.S. domestic markets, requiring constant conversion in international trading. A systematic 0.1% conversion error in a commodity trading desk processing millions of tons per month accumulates rapidly into meaningful P&L impact.

For consumers, weight conversion affects purchasing decisions in grocery shopping, shipping cost estimation, and recipe scaling. A recipe specifying 200g of butter requires a gram-based kitchen scale or a precise conversion to tablespoons (200g ÷ 14.2g per tablespoon = approximately 14 tablespoons). International shipping rate structures are based on weight in kilograms at international couriers, but the USPS uses pounds. Comparing costs requires accurate conversion. Nutritional analysis of a recipe requires knowing the gram weight of each ingredient even when measured by volume — which requires knowing density, but weight conversion is the starting point.

This converter covers common weight units including all metric SI prefixed units, avoirdupois imperial units (ounces, pounds, stones, short tons, long tons), metric tons, and troy ounces for precious metals. It does not cover some historical or highly specialized units that occasionally appear in technical literature: the grain (1/7000 pound = 64.799 mg, used in ballistics and pharmacy historically), the carat (200 mg exactly, used for gemstone weight — note this is different from gold 'karat' which measures gold purity), the hundredweight (cwt, which equals 100 lb in the U.S. but 112 lb in the UK), and the pennyweight (dwt = 1/20 troy ounce = 1.555 g, used in jewelry).

This converter handles mass/weight only — it does not perform density-based conversions between weight and volume. Converting '500 grams of flour to cups' requires knowing flour density, which varies with packing method. Converting 'liters of oil to kilograms' requires knowing the specific oil's density. These weight-to-volume conversions require density as an intermediate step and are not handled by a unit converter.

Note on 'weight' vs 'mass' in everyday use: this converter treats the terms interchangeably as is standard in everyday usage. In scientific and engineering contexts, mass (in kilograms) and weight (in newtons) are distinct quantities. The pound-force (lbf) is a unit of force/weight, while the pound-mass (lbm) is a unit of mass — the distinction matters in aerospace and mechanical engineering. This converter uses mass units throughout and does not convert between force and mass units.