Mass measures the fundamental quantity of matter contained in an object (expressed via F = m · a), whereas weight is the force exerted on that mass by gravitational acceleration (W = m · g). Across international commerce, logistics, healthcare, chemistry, jewelry, and aviation, mass measurement relies on two major systems: the International System of Units (SI metric: kilograms, grams, milligrams, metric tonnes) and US Customary / Imperial units (pounds, ounces, stones, short tons, long tons). Specialized fields also utilize carats (ct) for gemstones, troy ounces for precious metals, grains (gr) for ballistics, Daltons (Da) / atomic mass units (u) for chemistry, and Planck mass for quantum physics.
Our free online Weight and Mass Converter provides instant, high-precision conversions across all metric, imperial, commercial, gemstone, atomic, and astronomical mass units:
- Kilograms to Pounds: Multiply kg by
2.20462262(exact 1959 International Avoirdupois standard: 1 lb = 0.45359237 kg = 453.59237 g). - Pounds to Ounces: Multiply pounds by
16(1 lb = 16 oz; 1 oz = 28.349523125 g). - Gram to Milligrams: Multiply grams by
1,000(1 g = 1,000 mg = 1,000,000 μg). - Metric Tons to Kilograms: Multiply tonnes by
1,000(1 metric t = 1,000 kg = 2,204.623 lbs). - Short Tons (US) to Pounds:
1 US short ton = 2,000 lbs = 907.18474 kg. - UK Stone to Pounds / Kilograms:
1 UK stone = 14 lbs = 6.35029318 kg. - Carats to Milligrams: Multiply carats by
200(1 ct = 200 mg = 0.2 g).
Master Weight & Mass Unit Conversion Table
The table below displays exact physical relationships, SI power multipliers, and US Customary / Imperial equivalents relative to 1 Kilogram (kg):
| Mass Unit Name | Symbol | Exact Value in Kilograms (kg) | US Customary / Imperial Equivalent | Domain & System Standard |
|---|---|---|---|---|
| 1 Kilogram | kg |
1.0 kg |
2.204623 lbs (35.273962 oz) | SI Base Unit (2019 Planck Constant Definition) |
| 1 Gram | g |
0.001 kg (10-3 kg) | 0.035274 oz (0.002205 lbs) | SI Metric Everyday & Chemistry Unit |
| 1 Milligram | mg |
0.000001 kg (10-6 kg) | 0.015432 grains (gr) | Pharmaceutical Dosage & Analytical Chemistry |
| 1 Microgram | μg, mcg |
1.0 × 10-9 kg | 0.00001543 grains | Medical & Trace Nutrient Dosimetry |
| 1 Metric Ton (Tonne) | t, MT |
1,000.0 kg (1 Megagram) | 2,204.623 lbs (1.102311 short tons) | International Freight & Industrial Bulk |
| 1 Pound (Avoirdupois) | lbs, lb |
0.45359237 kg (exact) |
16.0 oz (453.59237 g / 7,000 grains) |
1959 International Pound Agreement Standard |
| 1 Ounce (Avoirdupois) | oz |
0.028349523125 kg (exact) |
1/16 lb (28.349523 g / 437.5 grains) |
US Customary Food & Postal Unit |
| 1 Short Ton (US Ton) | ton (US) |
907.18474 kg (exact) |
2,000 lbs (0.907185 metric tons) |
US Freight & Commercial Vehicle Standard |
| 1 Long Ton (UK Imperial Ton) | ton (UK) |
1,016.0469088 kg (exact) |
2,240 lbs (1.120 short tons) |
UK Imperial Shipping & Naval Displacement |
| 1 Stone (UK) | st, stone |
6.35029318 kg (exact) |
14.0 lbs (224 oz) |
UK & Ireland Body Weight Measurement |
| 1 Metric Carat | ct, car |
0.0002 kg (0.2 g) |
3.086472 grains (0.007055 oz) | 1907 CGPM Gemstone & Diamond Standard |
| 1 Troy Ounce | oz t |
0.0311034768 kg (31.103477 g) | 1.097143 oz avdp (480 grains) | Bullion Precious Metals (Gold, Silver, Platinum) |
| 1 Grain | gr |
0.00006479891 kg (64.79891 mg) | 1/7,000 lb (1/437.5 oz) | Ballistics Gunpowder & Arrow Mass |
| 1 Slug | slug |
14.59390294 kg | 32.174049 lbs | Imperial Gravitational Mass Unit (lbf·s²/ft) |
| 1 Unified Atomic Mass Unit (Dalton) | u, Da |
1.660539066 × 10-27 kg | 3.66086 × 10-27 lbs | 1/12th Mass of Unbound Carbon-12 Atom |
Step-by-Step Calculation Example
To convert a body weight of 75 Kilograms (75 kg) into Pounds (lbs) and Stones (st):
75 kg × 2.20462262 = 165.346696 Pounds (165.35 lbs)
165.346696 lbs ÷ 14 = 11.810478 Stones
0.810478 st × 14 lbs/st = 11.35 lbs
Thus, 75 kg is equal to 165.35 lbs (or 11 stone, 11.35 lbs).
Real-World Physical Mass & Scale Benchmarks
Below is a comparative reference chart showing masses across subatomic particles, biological organisms, vehicles, planets, and stars:
| Physical Scale / Object | Mass in Metric Units | Mass in US Customary / Scientific Units | Scientific & Everyday Context |
|---|---|---|---|
| Electron Rest Mass (me) | 9.1093837 × 10-31 kg | 0.00054858 Da (u) | Rest mass of an elementary lepton electron |
| Proton Rest Mass (mp) | 1.6726219 × 10-27 kg | 1.00727646 Da (u) | Rest mass of a subatomic baryon proton |
| Standard Metal Paperclip | 1.0 gram (g) | 0.035274 oz (15.43 grains) | Everyday 1-gram physical benchmark object |
| Standard US 5-Cent Coin (Nickel) | 5.0 grams (g) | 0.17637 oz (77.16 grains) | Official US Mint cupronickel coin specification |
| Average Adult Human Mass | 70.0 kilograms (kg) | 154.32 lbs (11.02 stone) | Global standard reference adult human mass |
| Mid-Size Passenger Car | 1,500 kilograms (1.5 t) | 3,306.9 lbs (1.653 short tons) | Curb weight of a modern mid-size sedan automobile |
| Boeing 747-400 Max Takeoff Weight | 396,890 kg (396.89 t) | 875,000 lbs (437.5 short tons) | Maximum commercial aircraft departure weight |
| Planet Earth Mass (M⊕) | 5.9722 × 1024 kg | 5.9722 Ronnagrams (Rg) | Total planetary gravitational mass of Earth |
| Sun Mass (M⊙) | 1.98847 × 1030 kg | 1.9885 Quettagrams (Qg) | Solar mass unit (333,000 Earth masses) |
History & Standards: 2019 Planck Constant Kilogram Redefinition vs. 1959 Avoirdupois Agreement
The 2019 Planck Constant Redefinition of the Kilogram
From 1889 until May 20, 2019, the kilogram (kg) was defined by a physical object: the International Prototype of the Kilogram (IPK), nicknamed “Le Grand K”, a cylinder of platinum-iridium alloy stored in a vault in Sèvres, France. Because IPK mass drifted over a century, the 26th CGPM voted unanimously to redefine the kilogram based on an unvarying physical constant of nature: the Planck constant (h = 6.62607015 × 10-34 J·s) measured via Kibble balance electro-magnetic force comparison.
The 1959 International Avoirdupois Pound Agreement
Before 1959, national standards bureaus in the US, UK, Canada, Australia, and New Zealand maintained slightly different definitions of the avoirdupois pound based on historical brass prototype weights. On July 1, 1959, the six nations signed the International Yard and Pound Agreement, standardizing the international avoirdupois pound to exactly 0.45359237 kilograms (1 lb = 453.59237 g) and the ounce to exactly 28.349523125 grams.
Popular direct conversions:
- Kilograms to Pounds Converter | Pounds to Kilograms Converter
- Grams to Ounces Converter | Ounces to Grams Converter
- Pounds to Ounces Converter | Ounces to Pounds Converter
- Grams to Pounds Converter | Pounds to Grams Converter
- Grams to Kilograms Converter | Kilograms to Grams Converter
- Grams to Milligrams Converter | Milligrams to Grams Converter
- Ounces to Kilograms Converter | Kilograms to Ounces Converter
- Pounds to Stone Converter | Stone to Pounds Converter
- Tons to Pounds Converter | Pounds to Tons Converter
- Conversion Calculator Main Directory
Frequently Asked Questions (FAQ)
How many pounds (lbs) are in 1 kilogram (kg)?
There are approximately 2.204623 pounds in 1 kilogram (or 2 lbs 3.27 oz) under the 1959 International Avoirdupois Agreement.
How many grams (g) are in 1 ounce (oz)?
There are exactly 28.349523125 grams in 1 avoirdupois ounce (or ~28.35 g).
What is the difference between a US Short Ton, UK Long Ton, and Metric Tonne?
A US Short Ton equals 2,000 lbs (907.185 kg). A UK Long Ton equals 2,240 lbs (1,016.047 kg). A Metric Tonne (t) equals 1,000 kg (2,204.623 lbs).
How many pounds are in 1 UK stone?
There are exactly 14 pounds in 1 UK stone (which equals 6.350293 kilograms).