Complete Weight Conversion Guide
Master professional weight conversion for medical dosing, jewelry appraisal, cooking precision, and scientific applications. Complete guide with real-world examples and expert techniques.
Table of Contents
1. Understanding Weight Units
Metric System
- Kilogram (kg): Base unit, 1,000 grams
- Gram (g): Standard for small items
- Milligram (mg): Medications, supplements
- Microgram (μg): Vitamins, trace elements
- Metric Ton (t): Heavy cargo, 1,000 kg
Imperial System
- Pound (lbs): US standard, 453.592g
- Ounce (oz): 1/16 pound, 28.35g
- Stone (st): UK body weight, 14 lbs
- US Ton: 2,000 pounds
- Imperial Ton: 2,240 pounds
Specialized Units
- Carat (ct): Gemstones, 200mg
- Troy Ounce: Precious metals, 31.1g
- Pennyweight: Gold/silver, 1.555g
- Grain (gr): Pharmaceuticals, 64.8mg
- Troy Pound: 12 troy ounces
Pro Tip: Context Matters
The same weight can be expressed differently depending on context. For example, 1 ounce of gold is actually a troy ounce (31.1g), not a standard ounce (28.35g). Always verify which system you're working with to avoid costly mistakes.
2. Conversion Basics
Essential Conversion Factors
Most Common Conversions:
- 1 kilogram = 2.20462 pounds
- 1 pound = 0.453592 kilograms
- 1 ounce = 28.3495 grams
- 1 gram = 0.035274 ounces
- 1 stone = 6.35029 kilograms
Quick Mental Math:
- • kg to lbs: multiply by 2.2
- • lbs to kg: divide by 2.2
- • oz to g: multiply by 30 (approx)
- • g to oz: divide by 30 (approx)
Step-by-Step Process
3. Precision Guidelines
Common Precision Mistakes
- • Using too many decimals for everyday applications (showing 68.0389 kg for body weight)
- • Using too few decimals for critical applications (2g instead of 2.15g for medication)
- • Confusing measurement precision with calculation precision
- • Not accounting for source measurement accuracy
4. Medical & Pharmaceutical Applications
Medication Dosing
Best Practices:
- • Always use metric units (mg, g, kg) for dosing
- • Body weight in kg for weight-based dosing
- • Precision: typically 2-3 decimal places
- • Double-check calculations with independent verification
Example: Pediatric Dosing
Child weight: 22 lbs → 10.0 kg
Medication: 15 mg/kg
Dose: 10.0 kg × 15 mg/kg = 150 mg
Laboratory Measurements
Common Lab Units:
- • Milligrams (mg): Blood glucose, medication levels
- • Micrograms (μg): Vitamin levels, trace elements
- • Grams (g): Protein, sample weights
- • mg/dL, μg/mL: Concentration units
Critical Conversions:
- 1 g = 1,000 mg = 1,000,000 μg
- 1 mg = 1,000 μg
- 1 grain = 64.8 mg (old pharmaceutical unit)
5. Jewelry & Precious Metals
Gemstone Weights
Carat System
1 carat = 200 milligrams = 0.2 grams
Common sizes:
- • 0.25 ct = 50 mg
- • 0.5 ct = 100 mg
- • 1.0 ct = 200 mg
- • 2.0 ct = 400 mg
Precious Metals
Troy Weight System
1 troy ounce = 31.1035 grams
Professional conversions:
- • 1 troy lb = 12 troy oz = 373.24g
- • 1 pennyweight = 1.555g
- • 20 pennyweights = 1 troy oz
Pricing Calculations
Example: Gold Price
If gold = $65/gram, what's the troy oz price?
$65 × 31.1 = $2,021.50/troy oz
⚠️ Warning
Never confuse troy ounces with regular ounces when dealing with precious metals - this is a $400+ error per ounce!
Ready to Practice?
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