Unit	= Kilograms	Notes
1 mg	0.000001	Milligram
1 grain	0.00006479891	Troy/Avoirdupois grain
1 g	0.001	Gram
1 oz	0.028349523	Avoirdupois ounce
1 lb	0.45359237	Avoirdupois pound
1 kg	1	SI base unit
1 stone	6.35029318	14 pounds
1 short ton	907.18474	US ton (2000 lb)
1 long ton	1016.0469	UK/Imperial ton (2240 lb)
1 tonne	1000	Metric ton

Common Engineering Mass Conversions

From → To	Multiply by	Example
kg → lb	2.20462	100 kg = 220.46 lb
lb → kg	0.45359	100 lb = 45.36 kg
oz → g	28.3495	1 oz = 28.35 g
g → oz	0.03527	100 g = 3.53 oz
tonne → short ton	1.10231	1 t = 1.102 short tons
short ton → tonne	0.90718	1 ST = 0.907 t
stone → kg	6.35029	10 stone = 63.5 kg

Handy Memorization Tips

• 1 kg ≈ 2.2 lb (for quick estimates)
• 1 lb ≈ 454 g
• 1 ounce ≈ 28.35 g
• 1 stone = 14 lb = 6.35 kg (used in UK for body weight)
• 1 tonne = 1000 kg ≈ 2205 lb
• 1 short ton (US) = 2000 lb ≈ 907 kg
• 1 long ton (UK) = 2240 lb ≈ 1016 kg
• 1 grain ≈ 64.8 mg (used in ballistics and pharmacy)

Mass vs Weight

In everyday use, “weight” and “mass” are used interchangeably, but they differ:

• Mass (kg, lb-mass) is the amount of matter — constant everywhere
• Weight (N, lbf) is the gravitational force — varies with location
• On Earth’s surface: Weight (N) = Mass (kg) × 9.81 m/s²
• A 100 kg mass weighs 981 N on Earth but only 163 N on the Moon

Application-Specific Units

• Balancing: Unbalance measured in g·mm (grams × millimeters) or oz·in (ounces × inches)
• Pharmacy: Grains (1 gr = 64.8 mg), drams, scruples
• Precious metals: Troy ounce (31.103 g) ≠ Avoirdupois ounce (28.350 g)
• Gemstones: Carat (1 ct = 0.2 g)