Weight Calculator

Convert between kg, lbs, stone, ounces, and tons, calculate weight as a force from mass and gravity (or the reverse), or find out what your Earth weight would translate to on the Moon, Mars, Jupiter, and every other planet.

For personal planning and general reference — verify important results when needed.

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Your Input

Select a conversion type, enter your weight or mass value, then click Convert or Calculate to get instant results with a detailed step-by-step solution.

Mass and weight are the same number only on Earth

Mass is a fixed property of an object — how much matter it's made of — and it doesn't change no matter where that object is. Weight is the force gravity exerts on that mass, and gravity varies by location, so weight changes even when mass doesn't.

Weight (force) = Mass × Gravitational acceleration

70 kg × 9.80665 m/s² ≈ 686.5 N (about 154.3 lbf) on Earth

Everyday speech treats "weight" and "mass" as interchangeable because everyone shares the same planet and the same gravity — the units even get mixed together, with a bathroom scale reporting kilograms even though it's technically sensing a force. The distinction only starts to matter once gravity is no longer a constant, which is exactly the situation the Weight on Planets mode is built for.

Common weight unit conversions

Weight and mass unit conversion factors
Unit Equivalent
1 kilogram2.20462 lb
1 stone14 lb
1 ounce28.3495 g
1 US (short) ton2,000 lb
1 metric tonne1,000 kg (≈2,204.6 lb)

The US short ton and the metric tonne look interchangeable but aren't — mixing them up on a shipping manifest or a materials spec is off by about 10%, which matters at any real scale.

What the same mass would weigh elsewhere

Every planet has its own surface gravity, so the same 70 kg of mass produces a very different weight reading depending on where it's standing.

Approximate weight of a 70 kg person on other worlds
Body Gravity vs. Earth 70 kg person would weigh
Moon~0.166×~11.6 kg
Mars~0.378×~26.5 kg
Jupiter~2.53×~177 kg

The calculation is the ratio of the two gravities applied to Earth weight — no different, mathematically, from converting between any other pair of units, just with gravitational acceleration standing in for a conversion factor.

Related conversions

For mass-specific unit conversions with a deeper look at troy vs. avoirdupois ounces and long tons, see the mass calculator. Pairing weight with a physical size gives you density — the density calculator covers that — and for body measurements more broadly, the height calculator covers the other common conversion people look up alongside weight.

Frequently Asked Questions

How is weight converted between units?

Weight (mass in everyday use) converts with fixed factors: 1 kg = 2.20462 lb, 1 stone = 14 lb, 1 oz = 28.3495 g. Use avoirdupois ounces for general weight.

What is the difference between pounds and kilograms?

Kilograms are SI mass units used worldwide in science. US customary pounds are common in everyday US weight — they differ by a factor of about 2.2.

Are US tons and metric tonnes the same?

No. A US short ton is 2,000 lb; a metric tonne is 1,000 kg (about 2,204 lb). Always confirm which ton a shipment or spec uses.

Why does body weight fluctuate daily?

Hydration, meals, and salt intake can shift scale readings by several pounds. Trend averages matter more than a single reading for tracking.

How do I use this weight calculator?

Enter a value and source unit, select the target unit, and click Convert. Equivalent weight in metric, imperial, and other units appears instantly.

Is weight really different from mass?

In physics, yes: mass is how much matter something contains, and weight is the force gravity exerts on that mass, calculated as W = m times g. In everyday conversation the two words get used interchangeably because everyone is standing on the same planet with the same gravity, so the distinction only becomes practical when gravity itself is the variable, like calculating weight on another planet.

Why would you weigh less on the Moon but the same on a scale that measures mass?

A bathroom scale actually measures the force your body exerts on it, which is weight, not mass directly, and it just displays that force converted into a mass reading assuming Earth-standard gravity. Your mass, the actual amount of matter in your body, stays the same everywhere. Move that same mass to the Moon, where gravity is about one-sixth as strong, and the force on the scale drops proportionally even though nothing about your body changed.

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