Kilograms to Pounds Converter

The kilograms-to-pounds converter is a free online tool that translates any mass between the metric kilogram (kg) and the imperial / US customary pound (lb) in either direction. Type a value into either the kilograms or pounds field and the other field updates instantly as you type. Because the international avoirdupois pound has been defined as exactly 0.45359237 kilograms since the 1959 international yard and pound agreement, the conversion factor carries zero measurement uncertainty, both directions are a single multiplication by a defined constant.

This page also shows the same value in grams (g) and ounces (oz) for everyday kitchen, postal, and shipping use, includes quick presets for body weights from 1 kg to 100 kg, and lets you swap the units, copy the result, or convert in your head with a simple rule of thumb.

Intro / What it does

The kilogram is the SI base unit of mass and is used in virtually every scientific, medical, and industrial context worldwide. The pound is the everyday unit of weight in the United States and is still used for body weight, grocery items, and freight in the UK, despite the UK having officially metricated most other measures. Converting between the two is therefore one of the most common numerical tasks in international trade, fitness tracking, and cross-border communication.

The two scales meet at one exact point: 1 lb = 0.45359237 kg. From this single definition:

• Forward: lb = kg × (1 / 0.45359237) = kg × 2.2046226218487757
• Inverse: kg = lb × 0.45359237

Both factors are exact by international statute (1959 agreement, codified by NIST SP 811, the BIPM SI Brochure, and the UK Weights and Measures Act 1985). Unlike most everyday unit conversions, there is no measurement uncertainty, the only rounding error comes from how many decimal places you choose to display.

The converter also surfaces grams (1 kg = 1000 g exactly) and ounces (1 lb = 16 oz exactly) so a single page covers the four mass units you will meet on food labels, bathroom scales, parcel labels, and gym apps.

How to use this tool

1. Type a value into the Kilograms (kg) field. The default is 50 kg, which is roughly the average body weight of an adult woman in many countries.
2. Watch the Pounds (lb) field update instantly as you type, using the exact factor 2.2046226218487757.
3. Or type a value into the Pounds field. The kilograms field updates using the inverse factor 0.45359237.
4. Read the bonus panels for grams and ounces, which update from the same source value.
5. Click the ⇌ swap button if you want to flip the input and output without retyping.
6. Click a Quick preset to jump to a common reference weight (1 kg, 50 kg, 75 kg, 100 kg, or 150 lb).
7. Click Copy kg, Copy lb, Copy grams, Copy ounces, or Copy result to put any value (or the combined pair) onto your clipboard.

The "Show your work" line in the result box spells out the arithmetic in the form <value> kg × (1 lb / 0.45359237 kg) = <value> lb, so a student or curious user can verify the conversion step by step rather than trusting a black-box number.

The formula

The kilogram-to-pound conversion is a single exact multiplication:

lb = kg × (1 lb / 0.45359237 kg)

Numerically:

lb = kg × 2.2046226218487757

The inverse direction is just as simple:

kg = lb × 0.45359237 kg/lb

A useful rearrangement that makes the math more obviously a unit cancellation:

       1 lb
kg ×, , , , = lb
     0.45359237 kg

The "1 lb" and "0.45359237 kg" carry the same physical dimension (they are both ways of expressing the same amount of mass), so the kg units cancel and only the lb units remain. This is the canonical form shown in the "Show your work" line of the converter.

For the bonus units:

g  = kg × 1000
oz = lb × 16

Both are exact by definition, the gram is one-thousandth of the kilogram, and the avoirdupois ounce is one-sixteenth of the avoirdupois pound.

Worked examples

Example 1: 1 kg in pounds. Using the exact factor: 1 × 2.2046226218487757 = 2.2046226218487757 lb. Rounded to four decimal places, 1 kg ≈ 2.2046 lb. This is the reciprocal of the 1959 definition and is the fundamental building block: a 1 kg bag of sugar weighs about 2.20 lb on a US kitchen scale.

Example 2: 100 kg in pounds. 100 × 2.2046226218487757 = 220.46226218487757 lb. Rounded to two decimal places, 100 kg ≈ 220.46 lb. This is the high end of "large adult" body weight and is the standard checked-bag weight allowance for many airlines.

Example 3: 150 lb in kilograms (the inverse direction). 150 × 0.45359237 = 68.0388555 kg. Rounded to two decimal places, 150 lb ≈ 68.04 kg. This is the typical reading on a US bathroom scale for someone who would be described as "about 68 kg" or "10 stone 9 lb" in British usage.

Example 4: 75 kg in pounds. 75 × 2.2046226218487757 = 165.34669663865816 lb. Rounded to two decimal places, 75 kg ≈ 165.35 lb. This sits at the high end of the "healthy" BMI range for a 1.80 m adult and is a useful reference weight for fitness calculators.

Example 5: The definition itself, 1 lb in kg. By the 1959 international yard and pound agreement, 1 lb = exactly 0.45359237 kg. This is the conversion factor in its most reduced form, and any kg ↔ lb calculator that disagrees with this value beyond the rounding of its display is incorrect.

Example 6: Bonus grams and ounces for 5 kg. 5 kg × 1000 g/kg = 5000 g. 5 kg in pounds is 5 × 2.2046226218487757 = 11.023113109243878 lb. In ounces that is 11.023113109243878 × 16 = 176.3698097479 oz, which is why a 5 kg bag of flour is sold as "5 kg" in Europe and "11 lb / 176 oz / 5 kg" on US import labels.

Where it shows up

Body weight and fitness. Bathroom scales in the US display pounds; scales elsewhere display kilograms. Fitness apps, BMI calculators, and gym weigh-ins routinely need to translate between the two. A 70 kg adult reads as "154.32 lb" on a US scale and as "70 kg" elsewhere; both numbers describe the same person.

BMI (Body Mass Index). Most BMI calculators in the US accept pounds and inches, while most international calculators accept kilograms and metres. Converting a metric BMI input to its imperial equivalent requires the exact 0.45359237 kg/lb factor; rounding to 0.45 introduces ~0.8% error which can move borderline readings between "normal" and "overweight" categories.

Luggage and air travel. Most international airlines quote baggage allowances in kilograms (23 kg, 32 kg, etc.). Travellers who weigh their bags in pounds need the kilogram equivalent before they check in. A 50 lb checked bag is 22.68 kg, comfortably under the 23 kg economy allowance but over a 20 kg budget-airline cap.

Shipping and freight. International courier services (FedEx, UPS, DHL, Royal Mail) calculate postage from a kilogram-based weight but display both units on the label. Customs declarations for cross-border parcels need both the kilogram and pound figure to avoid delays at the border.

International trade and wholesale. Goods shipped between metric-using and imperial-using countries are weighed in one system and priced or invoiced in the other. A pallet of 250 kg of coffee is "551.16 lb" on the US wholesale invoice.

Medical dosing. Some pharmaceuticals are dosed in milligrams per kilogram of body weight. A 150 lb patient weighs 68.04 kg, and a drug dose of 5 mg/kg means 340.2 mg for that patient, rounding 150 lb to "70 kg" introduces a 1.96 kg error that translates directly to a 9.8 mg dosing error.

Cooking and groceries. US recipes list flour and sugar in cups and ounces; European recipes list them in grams and kilograms. A 500 g pack of pasta is roughly 1.10 lb or 17.64 oz. Online recipe converters need the exact kg ↔ lb factor to avoid surprising readers with the wrong quantity.

Common mistakes

Rounding 2.2 introduces ~0.2% error. A common shortcut is "1 kg ≈ 2.2 lb". The exact factor is 2.2046226218487757, which differs from 2.2 by 0.0046226, about 0.21%. For a 100 kg person this is 0.46 lb, which most people won't notice. For a 10,000 kg shipment it is 46.22 lb, which a freight forwarder will notice. Use the exact factor for any professional, medical, or shipping context.

Confusing the avoirdupois pound with the troy pound. The international avoirdupois pound (used for body weight, groceries, shipping, and everyday commerce) is exactly 0.45359237 kg. The troy pound (used for gold, silver, and other precious metals) is exactly 0.3732417216 kg, about 17.6% lighter. A "pound" of gold is meaningfully less gold than a "pound" of flour. Never apply the kg ↔ lb factor from this page to a price quoted per troy pound; the result will be wrong.

Confusing mass (kg, lb) with force (kgf, lbf). Engineers sometimes write "kg" when they mean kilogram-force (the force exerted by one kilogram under standard Earth gravity, about 9.80665 N). The kilogram-force and the pound-force are related by 1 kgf ≈ 2.20462 lbf, but the underlying quantities are different. For mass conversion (the topic of this page), use the exact 0.45359237 kg/lb factor.

Forgetting that "lb" is both singular and plural. The abbreviation "lb" comes from the Latin "libra" (pound) and is the same for one pound or a thousand pounds. "5 lb" and "1 lb" use the same symbol; "lbs" is informal but is widely seen on US scales and shipping labels. The converter accepts decimal values such as "1.5 lb" or "150 lb" without complaint.

Applying the inverse formula to the inverse formula. kg = lb × 0.45359237 is correct. kg = lb × 0.45359237 × 0.45359237 is not, that would treat 0.45359237 as if it were both a multiplier and a divider. A common slip in spreadsheets is to divide by 2.2046 instead of multiplying by 0.45359237 to go from pounds to kilograms, which gives a result that is exactly wrong by a factor of (0.45359237)² ≈ 0.2058.

Treating the conversion factor as approximate. Because most everyday conversions (miles to kilometres, Fahrenheit to Celsius) carry rounding, users sometimes round 0.45359237 to "0.45" or "0.454". The exact value is exact, not measured, and carries no uncertainty at all. If your calculator is using 0.45, your kg values are off by ~0.8%, which compounds across many entries.

Confusing the kilogram (mass) with the kilogram (cuisine). Cooks sometimes refer to a "kilogram of flour" as if it were a measure of volume. The kilogram is a unit of mass (or weight under Earth gravity), not volume. A kilogram of flour and a kilogram of water occupy very different volumes because of different densities.

Frequently Asked Questions

What is the exact conversion factor between kilograms and pounds? One international avoirdupois pound is defined as exactly 0.45359237 kilograms by the 1959 international yard and pound agreement. Reciprocally, one kilogram equals exactly 1 / 0.45359237 = 2.2046226218487757 pounds. Both factors are exact by international definition, so neither carries measurement uncertainty, only display rounding.

Why does the United States still use pounds instead of kilograms? The US customary system retained the pound from British colonial usage. Although the Metric Act of 1866 legalised the metric system and the Metric Conversion Act of 1975 encouraged voluntary metrication, the US has never made the metric system mandatory for everyday commerce. As a result, body weight, groceries, and freight are still routinely weighed in pounds, and converting to kilograms is a daily task for international readers and scientists.

Is the kilogram-to-pound conversion ever approximate? No. The conversion factor is exact by international definition. The only source of error in any displayed number is how many decimal places the converter (or the reader) chooses to keep. To six decimal places, 1 kg = 2.204623 lb, which is more than 0.1 g of precision and exceeds the readability of any consumer scale.

What is a troy pound and why is it different? A troy pound is a unit of mass used for precious metals (gold, silver, platinum) equal to exactly 0.3732417216 kilograms, about 82% of an avoirdupois pound. The troy pound is divided into 12 troy ounces rather than the avoirdupois 16, and a troy ounce is heavier than an avoirdupois ounce. The kg ↔ lb conversion on this page uses the avoirdupois pound; never use it to convert gold or silver prices.

How many pounds is 70 kg? 70 kg × 2.2046226218487757 lb/kg = 154.3235835294143 lb. Rounded to one decimal place, 70 kg ≈ 154.3 lb. This is close to the average body weight of an adult man in many countries.

How many kilograms is 150 lb? 150 lb × 0.45359237 kg/lb = 68.0388555 kg. Rounded to one decimal place, 150 lb ≈ 68.0 kg. This is a common adult body weight and is the figure used in many US fitness apps.

Can I use this converter for medical dosing calculations? Yes, the factor is exact, so a dose of "5 mg per kilogram of body weight" translates without loss of precision. For a 68.04 kg patient (150 lb), the dose is 68.04 × 5 = 340.2 mg. Always verify the dose with the original prescription and a qualified clinician; the converter removes arithmetic error but not clinical judgement.

How accurate is the mental shortcut "1 kg ≈ 2.2 lb"? Accurate to within 0.21%. The exact factor is 2.2046226218487757; rounding to 2.2 leaves an error of 0.0046. For a 70 kg adult this is 0.32 lb, within the readability of any bathroom scale. For a 10,000 kg freight shipment it is 46.2 lb, which a logistics manager would notice. Use the mental shortcut for everyday estimates and the exact factor for shipping, medical, and scientific work.

What is the difference between kilograms and pounds? A kilogram is the SI base unit of mass, currently defined by a fixed value of the Planck constant (6.62607015 × 10⁻³⁴ J⋅s). A pound is a US customary and imperial unit of mass equal to exactly 0.45359237 kilograms. Both measure the same physical quantity (mass), and the conversion between them is a single multiplication by a defined constant.

Does the kilogram-to-pound conversion change in different countries? No. All countries that use either the kilogram or the pound use the same definitions. The 1959 international yard and pound agreement was signed by the United States, the United Kingdom, Canada, Australia, New Zealand, and South Africa, and the same value is codified by NIST in the US, by the BIPM in the SI Brochure, and by the UK Weights and Measures Act 1985. There is no "different" pound to worry about.

Why do some calculators give slightly different results? They are rounding to different numbers of decimal places, or they are using an out-of-date factor. The conversion is exact, so any difference is in the rounding, not the physics. Use a calculator (such as this one) that keeps at least six significant figures and uses the exact 0.45359237 kg/lb value.

What is the smallest weight this converter can resolve? The converter accepts decimal input to the limit of JavaScript number precision, about 15 significant figures. For everyday use the practical limit is the readability of the input field. The converter rounds the displayed result to six decimal places by default, which is more precise than any consumer scale can measure.

References

• NIST Special Publication 811, Guide for the Use of the SI Units. The US National Institute of Standards and Technology (NIST) reference for SI usage, including the exact 0.45359237 kg/lb international avoirdupois pound conversion factor codified from the 1959 international yard and pound agreement.
• BIPM SI Brochure, 9th edition (2019). For the Kilograms to Pounds Converter, Published by the Bureau International des Poids et Mesures. Documents the SI definitions and lists the international avoirdupois pound (0.45359237 kg) as a non-SI unit accepted for use with the SI.
• International Yard and Pound Agreement, 1959. Signed on 1 July 1959 by the United States, the United Kingdom, Canada, Australia, New Zealand, and South Africa. Fixed the international yard at exactly 0.9144 metres and the international avoirdupois pound at exactly 0.45359237 kilograms, resolving small (~0.0002%) differences between the historical US and UK pounds.
• Weights and Measures Act 1985 (UK). UK statute that adopts the 1959 yard and pound definitions for use within the United Kingdom and confirms the stone as exactly 14 pounds, the pound as exactly 0.45359237 kilograms, and the yard as exactly 0.9144 metres.
• NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. The US reference for commercial weighing devices. Specifies that commercial scales in the US must use the international avoirdupois pound (0.45359237 kg) for any trade that crosses a state or national border.