Free Pounds to Kg Converter

What is a pound? What is a kilogram?

The pound is the everyday unit of weight in the United States, and the abbreviation lb comes from libra, the Latin word for a balance or scales. The pound in daily use is the avoirdupois pound of 16 ounces. Its size was fixed once and for all by the International Yard and Pound Agreement of 1959, when the United States, the United Kingdom, and other countries agreed that 1 lb equals exactly 0.45359237 kg. Before that agreement, the pound had drifted slightly between countries; since 1959 it has been the same pound everywhere.

The kilogram is the base unit of mass in the International System of Units (SI), used across Europe and almost everywhere else. One kilogram is 1,000 grams. Since 20 May 2019 the kilogram has been defined through the Planck constant, a fixed value in nature, so it no longer depends on any physical object. A litre of water weighs about 1 kg, which makes the kilogram easy to picture: a 68 kg person weighs about as much as 68 litres of water.

Because the pound is now defined in terms of the kilogram, converting between them is exact arithmetic, not an approximation. The only rounding happens when the result is displayed — this converter shows four decimal places, far more precise than any bathroom scale.

How to use

1. Type a weight in pounds in the left box — the kilograms appear instantly on the right, with no button to press.
2. Or type in the kilograms box instead: both boxes are editable, and typing in either one updates the other at once.
3. Press Swap to flip the direction. The converted value carries over as the new starting number, so you can keep converting back and forth.
4. Read the result line for the full conversion, and the line under it for the rate: 1 lb = 0.45359237 kg. The table below also shows grams, handy for food labels.

Pounds to kg formula

Converting pounds to kilograms is a single multiplication with an exact factor:

kg = lb × 0.45359237

And the reverse direction multiplies by the reciprocal:

lb = kg × 2.2046226218

• kg — weight in kilograms
• lb — weight in pounds (avoirdupois pounds, the common pound)
• 0.45359237 — kilograms in one pound, exact by definition since 1959
• 2.2046226218 — pounds in one kilogram (1 ÷ 0.45359237)

A handy check: halving the pounds and subtracting 10 percent of the result lands close to the true kilograms — 150 lb halves to 75, minus 7.5 gives 67.5 kg, against the exact 68.0389 kg. If you need other units in one place, the general unit converter covers more units than any single page here.

Worked example

Pounds to kg conversion table

Kilograms are shown to four decimal places and grams to one. Every value is computed from the exact factor 1 lb = 0.45359237 kg.

Everyday benchmarks: US weights in kilograms

These are the conversions people actually look up, computed with the exact factor:

• Newborn baby, 7.5 lb — 3.4019 kg. US birth announcements give pounds and ounces; European ones give grams.
• Adult body weight — 150 lb is 68.0389 kg; 180 lb is 81.6466 kg; 200 lb is 90.7185 kg.
• Checked bag, 50 lb — 22.6796 kg, just under the 23 kg limit most European airlines print. A 70 lb heavy bag is 31.7515 kg.
• Carry-on, 15 lb — 6.8039 kg. Light by European standards, where 10 kg cabin bags are common.
• Dumbbells — 10 lb is 4.5359 kg; 25 lb is 11.3398 kg; 45 lb is 20.4117 kg. European dumbbells jump in 2 kg steps, so there is rarely an exact match.
• Gallon of water, about 8.34 lb — about 3.783 kg. A US gallon of water is a handy test weight because its weight is so well known.
• Pet food bag, 25 lb — 11.3398 kg. US pet food is sold by the pound; European bags are labelled in kilograms.

For the background on why Europe and the US ended up with different systems, read the metric vs imperial conversion guide for Europe.

Frequently asked questions

How many kg is 1 pound?

1 pound is exactly 0.45359237 kg, or 453.59237 grams. The value is exact because the pound has been defined in terms of the kilogram since the International Yard and Pound Agreement of 1959.

How do I convert pounds to kg by hand?

Multiply the pounds by 0.45359237. For example, 150 lb times 0.45359237 equals 68.0389 kg. A quick estimate is to halve the pounds and subtract 10 percent of the result: 150 lb halves to 75, minus 7.5 gives 67.5 kg, close to the exact 68.0389 kg.

How many kg is 150 lb?

150 lb is 68.0389 kg. If you see 150 lb on a US chart, a European chart would show about 68 kg for the same weight.

What is 200 lb in kg?

200 lb is 90.7185 kg. Two hundred pounds is a round number on US scales and gym charts, and 90.7185 kg is its exact metric equivalent.

Is a pound the same as a kilogram?

No. A pound is much smaller: it takes 2.2046 lb to make 1 kg. A kilogram is about the weight of a litre of water, while a pound is about the weight of a loaf of bread.

Why do gym weights in the US use pounds?

US gyms label plates and dumbbells in pounds, so a 45 lb plate is the standard big plate. In Europe the same plate is 20 kg. The two are close but not equal: 45 lb is 20.4117 kg, and 20 kg is 44.0925 lb.

How accurate is this pounds to kg converter?

It uses the exact legal factor, 1 lb equals 0.45359237 kg, with no rounding until the displayed result. Results are shown to four decimal places, which is far more precise than any bathroom or gym scale.

What is the difference between lb and lbs?

There is no difference in meaning: lb is the abbreviation for pound, from the Latin word libra, and lbs is simply its informal plural. Both mean the same unit, and this converter shows lb in its results.

Sources

• NIST Special Publication 811 — Guide for the Use of the International System of Units (SI).
• BIPM SI Brochure — The International System of Units, including the 2019 definition of the kilogram.
• International Yard and Pound Agreement, 1959 — 1 lb = 0.45359237 kg exactly.
• NIST Handbook 44, Appendix C — conversion factors for mass and weight.

Disclaimer: Results use the exact legal factor and are rounded to four decimals; a calibrated scale is the authority for medical, trade, or competition weighing.

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