Weight is one of the most commonly converted measurements in daily life. Whether you are following a European recipe that lists ingredients in grams, checking your luggage before an international flight, or tracking your gym progress in pounds versus kilograms, knowing how to convert between weight units saves time, money, and frustration. This guide covers everything you need to know about weight conversions, from the basic formulas to practical reference charts and real-world scenarios.
The Two Main Systems: Metric and Imperial
The world uses two primary systems for measuring weight. The metric system (grams, kilograms) is used by almost every country except the United States, Myanmar, and Liberia. The imperial system (ounces, pounds, stones) is still dominant in the US and used informally in the UK.
This divide creates daily friction. A British person talking about "losing a stone" confuses Americans. An American baker trying to follow a French recipe struggles with gram measurements. Understanding both systems is no longer optional — it is essential.
The Exact Conversion Factors
These are the precise, internationally agreed-upon conversion factors:
| From | To | Formula |
|---|---|---|
| 1 Kilogram | Pounds | 1 kg = 2.20462 lbs |
| 1 Pound | Kilograms | 1 lb = 0.453592 kg |
| 1 Ounce | Grams | 1 oz = 28.3495 g |
| 1 Stone | Pounds | 1 st = 14 lbs |
| 1 Gram | Milligrams | 1 g = 1,000 mg |
Quick Reference Chart: Common Weights
| Kilograms | Pounds | Stones | Common Context |
|---|---|---|---|
| 1 kg | 2.20 lbs | 0.16 st | Small bag of sugar |
| 5 kg | 11.02 lbs | 0.79 st | Laptop bag |
| 10 kg | 22.05 lbs | 1.57 st | Carry-on luggage limit |
| 23 kg | 50.71 lbs | 3.62 st | Standard checked bag limit |
| 70 kg | 154.32 lbs | 11.02 st | Average adult weight |
| 100 kg | 220.46 lbs | 15.75 st | Heavy luggage / gym weights |
Cooking and Baking Conversions
Cooking is where weight conversions matter most for precision. A cup of flour can weigh anywhere from 120g to 150g depending on how it is packed. Professional bakers always use weight measurements for consistency.
- 1 cup of all-purpose flour ≈ 120–130 grams
- 1 cup of granulated sugar ≈ 200 grams
- 1 tablespoon of butter ≈ 14 grams
- 1 pound of ground beef = 453.6 grams
- 1 ounce of chocolate = 28.35 grams
When converting recipes, remember that volume (cups, tablespoons) and weight (grams, ounces) measure different properties. A cup of feathers and a cup of lead occupy the same volume but have wildly different weights. Always use weight for dry ingredients when precision matters.
Fitness and Body Weight
Gym equipment and fitness tracking apps often use different units depending on the country. A barbell loaded with "two 20kg plates" weighs 40kg total (88.2 lbs). If your fitness app tracks in pounds but your gym uses kilogram plates, confusion is common.
Body weight tip: When tracking weight loss or muscle gain, stick to one unit system. Switching between pounds and kilograms creates false impressions. Losing 1 kg (2.2 lbs) sounds less dramatic than losing 2.2 lbs, even though they are identical.
Travel and Luggage
Airlines use kilograms for baggage limits almost everywhere except the US, where pounds are standard. A 23 kg checked bag limit equals 50.7 lbs. If you are flying from New York to London, your airline might quote 23 kg at check-in while your home scale shows pounds. Converting before you pack prevents expensive overweight fees at the airport.
Use Our Free Weight Converter
For instant, accurate conversions between any weight unit, use our free Weight Converter. Enter any value in kilograms, grams, pounds, ounces, milligrams, or stones, and see all other units update in real-time.
Written by Alex Morgan. Last updated August 2026.