Workshop converter
Weight Converter
Convert everyday mass, precious metal units, engineering units, tons, and historical measures, then learn why a troy ounce is heavier while a troy pound is lighter and why weight changes when gravity does.
Common conversions
Sage’s guided lesson
“Weight” is the everyday word, but mass is doing most of the work
This converter changes units of mass: grams, kilograms, pounds, ounces, stones, tons, troy units, carats, slugs, and selected historical measures. In ordinary conversation we call all of that weight, which works fine until physics arrives carrying a newton and asking very specific questions. I’ll show you the conversions, the naming traps, and why the same object can weigh less without losing any mass.
First, put everything on the same balance
The converter uses the kilogram as the common reference
Every supported unit has a relationship to the kilogram. The converter multiplies your starting amount by the kilograms in one starting unit, then divides by the kilograms in one target unit.
The basic pattern
base kilograms = starting amount × kilograms in one starting unitanswer = base kilograms ÷ kilograms in one target unitFor modern units, these relationships are fixed. One pound equals exactly 0.45359237 kilogram. One avoirdupois ounce is exactly one sixteenth of that pound. Historical units such as shekels, minas, and talents varied by period and place, so the converter labels those values as approximate.
One kilogram is 1,000 grams. One gram is 1,000 milligrams. One milligram is 1,000 micrograms. The prefix tells you the power of ten, which is refreshingly civilized.
Let’s do one by hand
Converting 50 pounds into kilograms
Multiply the pound amount by the exact factor 0.45359237 kilogram per pound.
Worked example
50 lb × 0.45359237 = 22.6796185 kg22.6796185 kg × 1,000 = 22,679.6185 gTo go back, divide by 0.45359237.
For a fast estimate, divide pounds by 2.2. Fifty pounds comes out near 22.7 kilograms. Random thought: why did the student bring a ladder to math class? To reach new heights in algebra. Anyway, back to things sitting on scales.
Physics has entered the workshop
Mass stays with the object; weight depends on gravity
Mass describes inertia and is measured in kilograms in SI. Weight in the physics sense is force: mass multiplied by the local gravitational acceleration. Its SI unit is the newton.
The force relationship
weight force = mass × local gravityW = m × g1 kg at standard gravity weighs 9.80665 NA 10 kilogram toolbox has the same mass on Earth, the Moon, or in orbit. Its gravitational weight depends on the local field. On the Moon it would weigh about one sixth as much. In orbit, a scale can read nearly zero because the toolbox and scale are falling together, even though gravity is still acting. It would still resist acceleration like the same 10 kilogram toolbox. It would not become a dainty little toolbox emotionally.
Commercial scales commonly display mass units even though they sense force. They are calibrated so that ordinary local gravity produces the expected mass reading.
The ordinary pound has a family tree
Avoirdupois is the system behind everyday US pounds and ounces
The avoirdupois pound contains 16 ounces and exactly 7,000 grains. One avoirdupois ounce contains 437.5 grains. The grain is the shared small unit that also appears in troy and apothecary systems.
| Unit | Relationship | Metric value |
|---|---|---|
| Grain | 1/7,000 lb | 64.79891 mg |
| Dram | 1/256 lb | 1.771845195 g |
| Ounce | 1/16 lb | 28.349523125 g |
| Pound | 16 oz | 0.45359237 kg |
The abbreviation “oz” needs context. An ounce can be avoirdupois mass, troy mass, or fluid volume. If the document matters, write enough information to identify which ounce is invited.
Gold and gemstones use different drawers
A troy ounce is heavier, but a troy pound is lighter
A troy ounce contains 480 grains and equals 31.1034768 grams. An avoirdupois ounce contains 437.5 grains and equals 28.349523125 grams. That makes the troy ounce about 9.7 percent heavier.
Here is the trick: a troy pound contains only 12 troy ounces, or 5,760 grains. An avoirdupois pound contains 16 ordinary ounces, or 7,000 grains. So the troy ounce is heavier, but the troy pound is lighter. Measurement apparently wanted one riddle built directly into commerce.
A metric carat is exactly 200 milligrams. The name is historically connected with carob seeds, but modern carats do not depend on finding unusually cooperative seeds.
Carat measures gemstone mass. Karat describes gold purity, with 24 karat representing nominally pure gold. They sound alike because language enjoys setting traps near expensive objects.
The bigger units split into rival teams
Hundredweight and ton can change size across the Atlantic
One stone is exactly 14 pounds. A US hundredweight is 100 pounds, while an Imperial hundredweight is 112 pounds. A US short ton is 20 US hundredweights, or 2,000 pounds. An Imperial long ton is 20 long hundredweights, or 2,240 pounds.
A metric tonne is exactly 1,000 kilograms, about 2,204.62 pounds. “Ton” without a qualifier is not enough for precise work.
| Unit | Definition | Kilograms |
|---|---|---|
| US short ton | 2,000 lb | 907.18474 kg |
| Metric tonne | 1,000 kg | 1,000 kg |
| Imperial long ton | 2,240 lb | 1,016.0469088 kg |
The slug is an engineering mass unit in the foot pound second system. One slug is the mass accelerated at 1 ft/s² by 1 pound force, about 14.5939 kilograms. It is not named because engineers were weighing garden pests, although that would be memorable.
The kilogram stopped depending on one very important lump
For more than a century, the kilogram was tied to a metal cylinder
The international prototype kilogram was a platinum iridium cylinder kept near Paris. Copies around the world were compared with it. The awkward part was philosophical and practical: if the official artifact gained or lost a microscopic amount, it was still exactly one kilogram by definition while every copy appeared to change.
On May 20, 2019, the kilogram was redefined by fixing the numerical value of the Planck constant. Instruments such as the Kibble balance can connect mechanical power with electrical measurements and realize the kilogram without treating one physical object as the final authority.
The definition changed to make the unit more stable and reproducible, not to change the size of a kilogram. Ordinary measurements stayed continuous while the foundation underneath them became much better science.
A display with four digits is not automatically wise
Scales sense force, compare it with calibration, and make assumptions
Load cells measure tiny deformations or electrical changes caused by force. Mechanical balances compare unknown mass with known mass. Either way, friction, vibration, air movement, temperature, off center loading, surface level, buoyancy, and calibration can affect the reading.
Sage’s weighing checklist
Place the scale on a stable, level surface.Zero or tare it before adding the item.Keep the load centered and within rated capacity.Allow the reading to settle and control drafts for small masses.Know the difference between display resolution and actual accuracy.This converter changes units; it does not calculate mass from volume unless density is known. A gallon of water, oil, paint, sand, and mercury do not have the same mass. Historical shekels, minas, and talents also varied, so their converter values are useful conventions, not a time machine with calibration papers.
High precision mass comparison accounts for the buoyant force of the surrounding air. Everyday scales usually ignore it because the effect is tiny for ordinary work, but metrology eventually notices everything.
The balance has settled
Class is over. It is officially cheese fries time.
You now know why this converter uses kilograms in the middle, why 50 lb equals 22.6796185 kg, and why physics separates mass from weight force.
You also know that troy ounces are heavier, troy pounds are lighter, short tons and long tons disagree, carats belong to gemstones, karats belong to purity, and the kilogram no longer depends on one guarded metal cylinder.
Quick answers
Weight and mass conversion questions
How many kilograms are in one pound?
One avoirdupois pound equals exactly 0.45359237 kilogram.
What is the difference between mass and weight?
Mass describes an object’s inertia and amount of matter. Weight is the force caused by gravity acting on that mass. In everyday trade, weight is also commonly used to mean mass.
Is a troy ounce the same as an ordinary ounce?
No. A troy ounce is about 31.1034768 grams, while an avoirdupois ounce is exactly 28.349523125 grams.
Why is a troy pound lighter than an ordinary pound?
A troy pound contains 12 troy ounces, while an avoirdupois pound contains 16 avoirdupois ounces. The troy ounce is heavier, but the troy pound has fewer ounces.
How many pounds are in a stone?
One stone equals exactly 14 avoirdupois pounds.
What is the difference between a short ton and a long ton?
A US short ton is 2,000 pounds. An Imperial long ton is 2,240 pounds. A metric tonne is exactly 1,000 kilograms, about 2,204.62 pounds.
How much is one carat?
One metric carat equals exactly 200 milligrams, or 0.2 gram.
Would the same object weigh less on the Moon?
Its mass would remain the same, but its weight force would be about one sixth of its Earth weight because lunar gravity is weaker.