1 pound in kg
1 × 0.45359237 = 0.45359237 kg exactly (0.45 kg at 2 decimals).
Pounds to Kilograms Converter: Convert lbs to kg Instantly
Use this pounds to kilograms converter to turn pounds (lb) into kilograms (kg), switch the direction for the kg to lbs conversion, and see the exact factor and arithmetic used. It also accepts pounds and ounces together, so a reading of 5 lb 8 oz converts in one step. If you only need a quick lb to kg figure, the table below covers common weights.
lbs to kg converter
Enter a value, pick the direction, and the result updates as you type. Nothing is uploaded; the math runs in your browser.
Enter a value above to see the conversion.
What this tool does not do: it does not give medical, health, weight-loss or BMI advice, and it does not claim legal-for-trade accuracy. It converts mass units only.
How to use the pounds to kg calculator
- Choose the direction. Pounds to kilograms is the default; press Swap direction to convert kilograms to pounds instead.
- Type the value in pounds (or kilograms). Use the optional ounces field when the weight includes whole pounds plus ounces, such as 5 lb 8 oz.
- Set how many decimal places you want to see, from 0 to 6. The default is 2.
- Read the kilogram (or pound) result, the reverse conversion, the factor used, and the arithmetic steps shown under the result. Use Copy result to paste them elsewhere, or Print summary for a paper copy.
Calculation method and formula
One avoirdupois pound equals exactly 0.45359237 kilogram. That figure is the international pound defined by the 1959 agreement among the national standards bodies of the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa, and it is the value carried in weight-and-measures references published by the U.S. National Institute of Standards and Technology (NIST). The same definition underpins every pounds to kilos figure on this page.
The formulas used by this page are:
- Kilograms = pounds × 0.45359237
- Pounds = kilograms ÷ 0.45359237 (equivalently, kilograms × 2.20462262184878…, an approximation)
- Total pounds = pounds + ounces ÷ 16 (1 pound = 16 avoirdupois ounces)
- Derived: 1 ounce = 0.028349523125 kg = 28.349523125 g exactly; 1 kg ≈ 2.20462262184878 lb.
Arithmetic is done with exact integer-scaled decimals, not binary floating point, so the product with 0.45359237 is exact before the display is rounded. Displayed numbers are then rounded half up to the decimal places you chose. The reverse factor is shown as an approximation because 1 ÷ 0.45359237 is a non-terminating decimal.
Method & sources
- Rule version
- —
- October 18, 2026
- Conversion factor
- 1 lb = 0.45359237 kg exactly (international avoirdupois pound)
- Reference starting points
- NIST Office of Weights and Measures, NIST Special Publication 811 (Guide for the Use of the International System of Units), NIST handbooks and weight-and-measures publications before relying on the page as a citation.
- Byline
- Varnda Editorial Team.
- Corrections
- If you believe a figure on this page is wrong, contact Varnda through the contact page published on varnda.com and include the page URL, the input you used and what you expected. No dedicated contact URL was confirmed.
Worked examples
Each example uses the same factor the calculator uses: 1 lb = 0.45359237 kg. Numbers shown to two decimals are rounded half up from the exact product.
100 lbs to kg
100 × 0.45359237 = 45.359237 kg (45.36 kg at 2 decimals).
150 lbs to kg
150 × 0.45359237 = 68.0388555 kg (68.04 kg at 2 decimals).
180 lbs to kg
180 × 0.45359237 = 81.6466266 kg (81.65 kg at 2 decimals).
200 lbs to kg
200 × 0.45359237 = 90.718474 kg (90.72 kg at 2 decimals).
70 kg to pounds
70 ÷ 0.45359237 = 154.3235835… lb (154.32 lb at 2 decimals).
Pounds and ounces to kg (5 lb 8 oz)
Total pounds = 5 + 8÷16 = 5.5 lb. Then 5.5 × 0.45359237 = 2.494758035 kg (2.49 kg at 2 decimals).
The 5 lb 8 oz reading is a hypothetical everyday example (a typical carry-on bag), not a legal standard.
Quick-reference tables
Common pounds-to-kilograms values, generated by the conversion engine rather than typed by hand.
| Pounds (lb) | Kilograms (kg) | In grams |
|---|
Unit equivalences derived from the same exact pound definition. Use these when you only need a single-step figure.
| From | To | Value |
|---|---|---|
| 1 pound (lb) | kilograms (kg) | 0.45359237 (exact) |
| 1 ounce (oz) | grams (g) | 28.349523125 (exact) |
| 1 pound (lb) | ounces (oz) | 16 (exact) |
| 1 kilogram (kg) | pounds (lb) | 2.20462262184878… (approximate) |
| 1 gram (g) | ounces (oz) | 0.0352739619… (approximate) |
| 100 grams (g) | ounces (oz) | 3.52739619… (approximate) |
Infographics: the factor and the units side by side
Each bar shows the share of a kilogram that a given number of pounds represents, using the exact factor.
1 lb
0.45 kg
2 lb
0.91 kg
2.2046 lb (reverse factor)
1.00 kg
✓ What this converter covers
- Pounds (lb) to kilograms (kg) with the exact 0.45359237 factor
- Kilograms back to pounds using the same definition
- Pounds plus ounces in a single step (16 oz = 1 lb)
- Display rounding from 0 to 6 decimal places, applied after exact arithmetic
- Quick-reference values generated from the same engine
✗ What it does not cover
- Troy pounds, apothecary ounces, short tons or long tons
- Shipping dimensional or volumetric weight
- BMI, body-fat, diet or medical interpretation of a weight
- Legal-for-trade or certified scale claims
- Currency or price conversion of any kind
Comparison scale: the pound, kilogram, ounce and gram on one relative scale. Bar lengths are proportional to mass in kilograms (longest bar = 1 kg = 1,000 g).
1 kilogram = 1,000 g
1,000 g
1 pound = 453.59237 g
453.59 g
1 ounce = 28.349523125 g
28.35 g
1 gram
1 g
Common mistakes when converting pounds to kilograms
- Multiplying when you should divide. To go from pounds to kilograms, multiply by 0.45359237. To go the other way, divide kilograms by 0.45359237 (or multiply by about 2.2046).
- Using 2.2 as the reverse factor. Rounding 2.20462262 down to 2.2 is fine for a rough estimate, but it loses about 0.2% and is visible at 100 lb (220.0 lb instead of 220.46 lb).
- Confusing ounces with a troy ounce. This page uses avoirdupois ounces (16 per pound). Troy ounces, used for precious metals, are heavier (about 31.1 g) and are not the same unit.
- Forgetting to combine pounds and ounces. 5 lb 8 oz is 5.5 lb, not 5.08 lb. Divide the ounces by 16 before adding.
- Rounding too early. Rounding the factor to 0.45 before multiplying changes the answer. This tool keeps the full 0.45359237 factor and rounds only for display.
- Reading the kilogram figure as medical advice. A conversion result is a mass in another unit only. Health decisions belong with a qualified clinician.
Frequently asked questions
How many kg in a pound?
One avoirdupois pound equals exactly 0.45359237 kilogram. That definition is the international pound agreed in 1959 and carried in weight-and-measures references such as NIST Special Publication 811 and NIST Handbook 44. Check those NIST pages for the current published text before citing the figure.
How to convert pounds to kg by hand?
Multiply the number of pounds by 0.45359237. Example: 150 lb × 0.45359237 = 68.0388555 kg, which is 68.04 kg when you keep two decimals. If your weight is given in pounds and ounces, first add ounces ÷ 16 to the pounds, then multiply.
What is the pounds to kg formula?
Kilograms = pounds × 0.45359237. The reverse formula is pounds = kilograms ÷ 0.45359237. Both use the same exact conversion factor; the reverse factor 2.20462262184878… is only an approximation of 1 ÷ 0.45359237.
Is 1 pound the same as 1 kilogram?
No. A kilogram is heavier. About 2.2046 pounds make one kilogram, so 1 pound is only about 0.4536 kilogram.
How do I convert 5 lb 8 oz to kilograms?
Convert the ounces to pounds first: 8 oz ÷ 16 = 0.5 lb. Add that to 5 lb to get 5.5 lb. Then 5.5 × 0.45359237 = 2.494758035 kg, or 2.49 kg at two decimals. The ounces field on this page does that step for you.
Why do different websites show slightly different results?
Many sites round the factor to 0.45 or 2.2, or they round intermediate steps. Differences of a few hundredths of a kilogram usually come from that early rounding. This page multiplies by the full 0.45359237 and rounds only the final display.
Can I use this for shipping or cooking measurements?
Yes for ordinary mass conversion in cooking, travel, fitness logs or international paperwork. Check carrier rules separately if a shipment is priced by dimensional (volumetric) weight, and note that recipes sometimes use cup or spoon volumes, which this tool does not convert.
Does this tool give health or BMI advice?
No. It converts units of mass only. It does not calculate BMI, body fat, ideal weight or diet targets, and it is not a medical tool.
Glossary
- Avoirdupois pound
- The everyday pound used for most goods in the United States, defined as exactly 0.45359237 kg. Distinct from the troy pound used for precious metals.
- Ounce (oz)
- One sixteenth of an avoirdupois pound, exactly 28.349523125 grams.
- Kilogram (kg)
- The base unit of mass in the International System of Units (SI). One kilogram is about 2.2046 lb.
- Gram (g)
- One thousandth of a kilogram, exactly 0.01 kg.
- International yard and pound agreement (1959)
- The agreement among national standards bodies that fixed the pound at 0.45359237 kg exactly, which this page uses as its conversion factor.
- Exact vs approximate
- Exact means the value follows from the definition with no rounding (for example 1 lb = 0.45359237 kg). Approximate means the decimal continues or depends on rounding (for example 1 kg = 2.20462262184878… lb).
The conversion factor 1 lb = 0.45359237 kg is the international avoirdupois pound definition that appears in U.S. weight-and-measures literature. No live source was opened, so treat every citation below as a starting point to re-check, not as a quote from a page we verified today.
- NIST Office of Weights and Measures (OWM) — the U.S. agency responsible for weights and measures policy and SI guidance.
- NIST Special Publication 811, Guide for the Use of the International System of Units — conversion-factor tables, candidate source for the pound-to-kilogram factor.
- NIST Handbook 44 and Handbook 130 — weight-and-measures handbooks published by NIST OWM.
- NIST metric and unit-conversion resources — further conversion materials from OWM.
Status of these citations: NOT VERIFIED. Open the pages, confirm the factor, and update the rule version before treating the page as an authoritative citation.
Limitations, exclusions and assumptions
- Mass conversion only. No health, medical, BMI, diet or body-composition interpretation is provided or implied.
- Troy pounds, troy ounces, short tons, long tons and metric tonnes are different units and are out of scope unless a separate tool is built for them.
- Shipping dimensional (volumetric) weight is out of scope; carriers use their own divisors.
- Results are not certified for legal-for-trade weighing. Commercial scales are regulated separately under NIST Handbook 44 and state weights-and-measures programs.
- The pound definition itself is presented from general knowledge and flagged for verification above.
- Displayed values are rounded half up to the decimal places you select. Internal arithmetic stays exact; a rounded display can differ from another site that rounds differently.
- Inputs are stored in your browser only if you press the remember button. Clearing them removes the local copy this page created.
Summary: convert pounds to kilograms with the exact factor
This free pounds to kilograms converter multiplies pounds by the exact international factor 0.45359237 to give kilograms, reverses the conversion for kilograms to pounds, accepts pounds-and-ounces readings, and shows the arithmetic so you can check it. It covers cooking, shipping paperwork, travel, fitness logs and forms that ask for metric mass, and it stays inside a narrow, documented scope: unit conversion only.
