Weight Converter: Convert Between All Weight Units
The Weight Converter converts between all major units of weight measurement instantly in your browser. Whether you're converting inches to centimeters, pounds to kilograms, Fahrenheit to Celsius, or fluid ounces to liters, the tool handles all standard and metric units with precision.
Ready to convert? Open the tool and enter your value.
Open Weight Converter ↗Metric vs Imperial Unit Systems
The world uses two primary systems: the International System of Units (SI/metric), used by most of the world, and the imperial system, primarily used in the United States, Myanmar, and Liberia. The metric system is based on powers of 10, making conversions between metric units straightforward (1 kilometer = 1,000 meters). Imperial units use irregular conversion factors (1 mile = 1,760 yards = 5,280 feet).
Science, medicine, and international trade use metric universally. US everyday life and some UK contexts use imperial. Engineers in the US work in both depending on the industry — aerospace and medicine use metric, construction and manufacturing often use imperial.
How to Use the Tool
Type the numeric value you want to convert in any input field. The tool instantly shows the equivalent in all other weight units simultaneously.
Some converters show a dropdown for the source unit. Select your input unit and the conversion updates all outputs.
Every unit is shown simultaneously — you don't need to convert one pair at a time. Scan all values to find the one you need.
Click on any result to copy it to your clipboard.
Common Conversions Reference
Memorizing a few anchor conversions makes mental estimation fast:
- 1 inch = 2.54 cm (exact)
- 1 foot = 30.48 cm
- 1 mile ≈ 1.609 km (or roughly 1.6)
- 1 pound ≈ 0.454 kg (or roughly 0.45)
- 1 kg ≈ 2.205 pounds
- 0°C = 32°F, 100°C = 212°F
- 1 US gallon ≈ 3.785 liters
- 1 fl oz ≈ 29.57 ml
Conversion Formulas
Temperature conversions (the only non-linear ones):
Celsius to Fahrenheit: F = (C × 9/5) + 32
Fahrenheit to Celsius: C = (F − 32) × 5/9
Celsius to Kelvin: K = C + 273.15All other unit conversions are linear — multiply by a fixed factor:
cm to inches: value × 0.3937
kg to lbs: value × 2.2046
km to miles: value × 0.6214
liters to gal: value × 0.2642Practical Tips
- Cooking conversions — most recipe conversions involve volume (tablespoons, cups, liters) and weight (grams, ounces). Weight-based recipes are more accurate than volume-based ones for baking.
- Body measurements — US clothing uses inches; European sizing uses centimeters. For shoes, sizes are also country-specific and don't map cleanly to metric units.
- Scientific notation — for very large or small values, use the numeric keypad with E notation (e.g. 1.5e6 for 1.5 million).
- Significant figures — the tool shows high-precision decimal results. Round to the appropriate significant figures for your use case.
Real-World Use Cases
Cooking and Recipes
International recipes often use weight measurements instead of volume — grams and ounces for ingredients like flour, butter, and chocolate. Weight measurements are more accurate than cups and tablespoons because density varies. A US recipe calling for "2 cups of flour" is roughly 240–250g, but a British recipe specifying 250g is exact. When baking from an international recipe, convert using precise gram-to-ounce ratios: 1 oz = 28.3495g.
Fitness and Health
BMI (Body Mass Index) calculations require weight in kilograms and height in meters. If you know your weight in pounds and height in feet/inches, convert first: divide pounds by 2.205 for kilograms. BMI = weight(kg) / height(m)². A BMI between 18.5 and 24.9 is considered healthy range by most health organizations, though BMI has well-documented limitations as a sole health metric.
Gym equipment in the US uses pounds; equipment in most of the world uses kilograms. Knowing that 1 kg ≈ 2.205 lb makes quick mental conversions easier — 100 kg is about 220 lbs, 80 kg is about 176 lbs.
Shipping and Logistics
International shipping rates are calculated in kilograms. US domestic shipping often uses pounds and ounces. If shipping a package that weighs 3 lbs 4 oz internationally, convert to kg (1.474 kg) to get an accurate international rate quote. Many carriers also use "dimensional weight" — volume divided by a divisor — which may exceed actual weight for large light packages.
Scientific and Medical
Drug dosages are typically calculated in mg/kg of body weight. Converting patient weight from pounds to kilograms is a routine and safety-critical step in clinical settings. A 154 lb patient weighs 70 kg; a 220 lb patient weighs 100 kg. Medication dosing errors from unit confusion are a documented patient safety concern — always verify conversions in medical contexts.