Moving between kilograms, pounds, ounces, stone, and tons is something almost everyone does at least once a week — reading a UK recipe that lists flour in grams, checking a US nutrition label in ounces, weighing luggage at the airport, or interpreting a body-weight chart that mixes stone and pounds. This weight converter calculator does the math instantly using the exact international avoirdupois definitions, so you never have to trust a mental approximation again.
Type a number, pick your starting unit and your target unit, and the result card shows the converted value plus its equivalent in kilograms, pounds, and ounces. Whether you are shipping a package, baking a cake, tracking a fitness goal, or comparing grocery prices per pound versus per kilogram, the numbers on this page match what a scale or a customs form would tell you.
How to Use
- Enter the Weight Value you want to convert. It must be zero or a positive number — the calculator rejects negatives because mass cannot be negative.
- Choose the From Unit —
mg,g,kg,oz,lb,stone, orton(US short ton). The default is kilograms, which is the base SI unit. - Choose the To Unit — the same list. The result updates as soon as you change either dropdown.
- Read the Converted Weight on the result card. Below it you will see the same mass expressed in kilograms, pounds, and ounces, which is useful when a label uses one unit but your recipe or baggage allowance uses another.
- To reverse the conversion, click the swap icon between the two dropdowns — kilograms to pounds becomes pounds to kilograms in one click.
The engine treats all units as linear multiples of the kilogram, so the conversion is exact up to floating-point precision. There is no rounding step hidden in the math; the four displayed values are derived from the same underlying kilogram figure.
The Conversion Table Behind the Calculator
Every weight in this tool is first converted into kilograms, then divided into the target unit. The exact factors are fixed by international agreement:
- 1 milligram (mg) = 0.000001 kg
- 1 gram (g) = 0.001 kg
- 1 kilogram (kg) = 1.0 kg (the SI base unit)
- 1 ounce (oz, avoirdupois) = 0.028349523125 kg — exactly 1/16 of a pound
- 1 pound (lb, avoirdupois) = 0.45359237 kg — defined in 1959 and used by the US, UK, and most of the world
- 1 stone (st) = 14 lb = 6.35029318 kg — still common for body weight in the UK and Ireland
- 1 short ton (US ton) = 2000 lb = 907.18474 kg — do not confuse with the metric tonne (1000 kg) or the imperial long ton (2240 lb)
Two ratios worth memorizing: 1 kg ≈ 2.20462 lb and 1 lb = 16 oz exactly. If you only remember the first one, you can do a quick sanity check on any result this page produces.
Examples
Example 1 — Kilograms to pounds for body weight. A 70 kg person checks their weight on a US scale. Enter 70, from kg, to lb: the result is 154.32 lb, or about 11 stone 0.3 lb. If that person is on a fitness plan aiming to lose 5% of body weight, the target drop is 3.5 kg (about 7.7 lb) — a concrete number you can set on a scale rather than a vague "a few pounds."
Example 2 — Ounces to grams at the grocery store. Coffee priced at $12.99 per 12 oz bag works out to how much per gram? Convert 12 oz to grams: the result is 340.2 g, so the price is roughly $0.038 per gram. Compare that with a 250 g bag listed at $9.99 (about $0.040 per gram) and the larger bag is actually slightly cheaper per unit — but only once you convert ounces to grams can you see it.
Example 3 — Pounds to kilograms for shipping. A parcel weighed at the post office is stamped 42 lb. The courier's website charges by the kilogram and the limit before the next rate band is 20 kg. Convert 42 lb: the result is 19.05 kg, which fits under 20 kg — no extra oversize fee. At 43 lb the parcel becomes 19.5 kg, still under the limit; at 45 lb it crosses to 20.4 kg and triggers the next tier.
Example 4 — Stone to pounds for a UK weigh-in. A patient chart reads 12 st 6 lb. Convert 12 stone to pounds: that is 168 lb, plus 6 lb = 174 lb, which is about 78.9 kg. Doctors in the UK often record body weight in stone and pounds, while clinical guidelines use kilograms — this converter bridges the two systems in one step.
Example 5 — Tons to kilograms for freight. A small truck hauls 3 short tons of gravel. Convert 3 ton to kg: the result is 2721.6 kg (about 2.72 metric tonnes). If the bridge limit is 3 tonnes, the load is safe; if it is 2.5 tonnes, you need to split the delivery. Note that a US short ton (2000 lb) is roughly 907 kg, not the 1000 kg of a metric tonne — a difference of nearly 10% that matters for legal weight limits.
FAQ
How do I convert kilograms to pounds?
Multiply the kilogram value by 2.20462. For example, 70 kg × 2.20462 = 154.32 lb. This calculator does the same thing in both directions, so entering 154.32 lb and converting to kg gives back 70 kg.
How many ounces are in a pound?
There are exactly 16 ounces in one avoirdupois pound. This is the ounce used on US food labels and in everyday shopping. It is not the troy ounce (used for precious metals), which is about 31.1 g rather than 28.35 g.
What is a stone and how much is it in pounds?
A stone is an imperial unit still widely used for body weight in the UK and Ireland. One stone equals exactly 14 pounds, or 6.35029 kilograms. So 11 stone is 154 lb, and 12 stone 6 lb is 174 lb.
What is the difference between a ton and a tonne?
A US short ton is 2000 lb (about 907 kg). A metric tonne is 1000 kg (about 2204.6 lb). A UK long ton is 2240 lb (about 1016 kg). They differ by roughly 10%, so always check which "ton" a freight, bridge, or shipment document refers to. This calculator uses the US short ton.
How accurate is this weight converter?
The conversion factors are defined to more than 9 significant figures by international agreement (the 1959 International Yard and Pound Agreement). The displayed results are rounded to a sensible number of decimal places for readability, but the underlying math is exact to floating-point precision — equivalent to what a calibrated reference scale would report.
Can I use this for medicine or cooking?
Yes for cooking — recipe scaling in grams, ounces, and pounds is exactly what this tool is built for. For medicine, always follow the dose on the packaging or the instructions from a clinician; pediatric doses in particular should never be rounded down from a converted weight.
Is there a fee or sign-up required?
No. The calculator runs entirely in your browser, stores no data, and does not require an account. You can use it as many times as you like on a phone, tablet, or desktop.
Disclaimer
This weight converter calculator is provided for informational purposes only and does not constitute medical, shipping, legal, or trade advice. Conversion factors are based on the international avoirdupois system and are accurate for everyday use, but calibrated scales, customs authorities, airlines, and healthcare providers may use slightly different rounding conventions for fees, tariffs, or clinical dosing. Always confirm measured weights on a calibrated scale and verify any legal, medical, or commercial limits directly with the relevant authority before relying on a converted figure.