Mass & Weight Converter

High-precision mass and weight converter. Convert between metric, imperial, atomic, and astronomical units.

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Designed for everyone from home cooks to astrophysicists, this calculator handles everyday and extreme values flawlessly:

  • Scientific Notation: You can type values like 6.022e23 or 5E-10 directly into the input box for atomic or cosmic scales.
  • Instant Swapping: Click the arrows in the middle to instantly reverse the conversion direction.

Mass vs. Weight: What's the Difference?

In everyday conversation, we use "mass" and "weight" interchangeably, but in physics, they are entirely different concepts.

Mass is a measure of how much matter an object contains (measured in Kilograms). It is intrinsic and never changes. Weight is a measure of the gravitational force pulling on that mass (measured in Newtons or Pounds-force).

"If you travel to the Moon, your mass remains exactly the same, but your weight drops to about 16.5% of what it is on Earth because the Moon's gravity is much weaker."

Scientific & Astronomical Scales

For chemistry, physics, and astronomy, standard units like kilograms become cumbersome. We support specialized units:

  • Atomic Mass Unit (u): Used in chemistry. It is defined as exactly 1/12 of the mass of a carbon-12 atom.
  • Earth Mass (M⊕): Used to measure rocky exoplanets. 1 M⊕ ≈ 5.97 × 10^24 kg.
  • Solar Mass (M☉): Used to measure stars and black holes. 1 M☉ ≈ 1.99 × 10^30 kg.

Cooking Conversions Cheat Sheet

1 Ounce (oz)≈ 28.35 Grams
1 Pound (lb)454 Grams
1 Kilogram (kg)2.205 Pounds
1 Stone14 Pounds

Frequently Asked Questions

How do I easily convert kilograms to pounds in my head?

Multiply the kilograms by 2, and then add 10% of that result. For example, 50 kg × 2 = 100. 10% of 100 is 10. Total: 110 lbs. (The exact answer is 110.23 lbs).

What is the difference between a Troy Ounce and a regular Ounce?

A standard (avoirdupois) ounce is 28.35 grams, commonly used for food and mail. A Troy Ounce is heavier, at exactly 31.1034768 grams, and is used strictly for weighing precious metals like gold and silver.

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