Weight Converter

About this calculator

Shipping paperwork mixes units. A supplier quotes grams, a scale reads kilograms, an international rate card is in pounds, and a freight quote is in tonnes. Converting between them by memory is where a decimal point goes missing.

This converter uses the same unit table the shipping calculators on this site use, so a weight converted here is the weight those tools will bill on. Every other unit is shown alongside the one you asked for, because a parcel is rarely quoted in only two.

How to use this calculator

1. Enter the weight you have.
2. Choose the unit it is in, and the unit you want.
3. Read the conversion, with the remaining units listed underneath.

The formula

Every weight is converted to kilograms first and then out again, so no pair of units needs its own factor and no pair can disagree with another.

1 kg = 1,000 g = 1,000,000 mg = 0.001 t
1 lb = 0.45359237 kg   (exact by definition)
1 oz = 1/16 lb = 0.028349523125 kg

The pound is defined as exactly 0.45359237 kilograms by international agreement, and the ounce as exactly one sixteenth of a pound. These are definitions rather than measurements, so the conversions are exact to as many decimal places as you care to read.

Worked example

A parcel weighing 2.5 kg, quoted to a carrier who prices in pounds:

2.5 kg / 0.45359237 = 5.51156 lb

A carrier billing whole pounds would charge 6 lb, so the rounding matters more than the conversion does.

Notes and limits

• The tonne here is the metric tonne of 1,000 kg, not the US short ton or the UK long ton.
• Ounces here are ounces of weight (avoirdupois), not fluid ounces.
• Couriers round the billed weight up to a slab after converting, so convert first and round second - doing it the other way round costs you a slab.
• Six decimal places are shown because a conversion into grams or milligrams needs them. Your courier will not bill to that precision.

What this calculation assumes

• The tonne is the metric tonne of 1,000 kg.
• The ounce and pound are the avoirdupois units used in trade.
• Factors are exact by definition, not rounded approximations.