Weight Converter
Convert between metric, avoirdupois and troy units of mass using exact internationally agreed factors — including the troy system used for precious metals.
Weight Converter
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: Mass conversion routes through the kilogram, the SI base unit. The pound is defined as exactly 0.45359237 kg by the 1959 International Yard and Pound Agreement, which makes all avoirdupois conversions exact. Troy units, used for precious metals, follow a different and incompatible scale.
Formula
Each factor is the number of kilograms in one unit of that type.
Worked Example
- Start from the base unit. One kilogram is 1 kg by definition.
- Identify the target factor. One pound is exactly 0.45359237 kg.
- Divide. 1 ÷ 0.45359237 = 2.2046226 lb.
- Check a reverse case. 150 lb × 0.45359237 = 68.038856 kg.
- Note the troy difference. One troy ounce is 0.0311034768 kg, about 10% heavier than the avoirdupois ounce of 0.028349523125 kg.
Metrology note. The troy and avoirdupois systems are genuinely incompatible: a troy ounce is heavier than a standard ounce, but a troy pound is lighter than a standard pound, because a troy pound contains only 12 troy ounces rather than 16. Confusing the two is a well-known source of error in precious metal trading.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Precious metals and bullion
Gold, silver and platinum are quoted per troy ounce, not the ordinary ounce. A one-ounce gold coin contains 31.1034768 g, roughly 10% more than a 28.35 g avoirdupois ounce, so the distinction has direct financial consequences.
Shipping and freight
Short tons, long tons and metric tonnes differ by up to 12%. Freight quotes, customs declarations and load limits must specify which is meant, and this engine converts between all three exactly.
Cooking and nutrition
Recipes crossing between systems need gram-level accuracy for baking, where ratios matter. The Cooking Measurement Converter handles volume-based kitchen units.
Methodology & Editorial Standards
All factors express the exact number of kilograms per unit. The avoirdupois pound is exactly 0.45359237 kg under the 1959 International Yard and Pound Agreement, from which the ounce, stone and ton derive exactly. Troy units follow the separate troy scale, where one troy ounce is exactly 0.0311034768 kg and a troy pound contains 12 troy ounces. The carat is exactly 200 mg. Note that this engine converts mass, not weight in the physical sense of force. All conversion factors are exact by definition under the International System of Units, or exact by international agreement where the unit is defined by treaty. Values are held at full IEEE-754 double precision internally and rounded only for display, so chained conversions do not accumulate drift.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Weight Converter — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many pounds are in a kilogram?
Exactly 2.2046226 lb to eight significant figures. The relationship is exact by definition because one pound is defined as exactly 0.45359237 kg.
What is the difference between mass and weight?
Mass is the quantity of matter, measured in kilograms and constant everywhere. Weight is the force gravity exerts on that mass, measured in newtons and varying with location. Everyday usage conflates them; this engine converts mass.
What is a troy ounce?
The standard unit for precious metals, exactly 31.1034768 g — about 10% heavier than the avoirdupois ounce of 28.349523125 g. Gold, silver, platinum and palladium are all priced per troy ounce.
Why is a troy pound lighter than a normal pound?
Because a troy pound contains 12 troy ounces rather than 16 avoirdupois ounces. A troy pound is 373.2417216 g against 453.59237 g for the standard pound, despite the individual troy ounce being heavier.
How many kilograms are in a stone?
Exactly 6.35029318 kg, since a stone is 14 pounds. The unit remains in common use for body weight in the United Kingdom and Ireland.
What is the difference between a US ton and a metric tonne?
A US short ton is 2,000 lb or 907.18474 kg. A metric tonne is exactly 1,000 kg. A UK long ton is 2,240 lb or 1,016.0469088 kg. The three differ by up to about 12%, which matters considerably in freight.
What is a carat?
For gemstones, exactly 200 milligrams. It is distinct from karat with a K, which measures gold purity in 24ths — 18 karat gold is 18/24 or 75% pure gold by mass.
What is a grain?
The smallest traditional unit in both troy and avoirdupois systems, exactly 64.79891 mg. It survives in ammunition, arrow and some pharmaceutical measurements.
Is the kilogram still defined by a physical object?
No. Since 2019 the kilogram has been defined by fixing the numerical value of the Planck constant. The platinum-iridium prototype in Sèvres was retired, ending the last physical artefact definition in SI.
How do I convert kg to lbs mentally?
Double the kilograms and add ten percent. For 80 kg: 160 plus 16 gives 176, against the exact 176.37 lb. The approximation runs about 0.2% low, which is close enough for most everyday purposes.
Are pounds and pounds-force the same?
No. The pound-mass is a unit of mass; the pound-force is the weight of one pound-mass under standard gravity, about 4.448 newtons. Engineering contexts distinguish them carefully, and confusing them is a classic source of error.
Why do recipes need mass rather than volume?
Because volume measurement of solids is unreliable — a cup of flour can vary by 20% depending on how it is packed. Professional baking uses mass for exactly this reason, and ratios by mass are reproducible.
Is this weight converter free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.
Which currency does it use?
Amounts display in US$ accounting format, but the underlying mathematics is currency-agnostic. The result is identical in any currency, so simply read the figures in your own.
Why does a result show an em-dash?
An em-dash indicates the calculation is not defined for the inputs given — typically a division by zero or a value outside the valid domain. We show a dash rather than a misleading number.
How do I report an error?
Email apexconverter.praxiscalc@gmail.com with the tool URL, your exact inputs, the output received and the output you expected. Verified mathematical errors are patched within 72 hours.