Lbs to kg Converter

The pound and the kilogram share daily life whether you want them to or not. American gym equipment lists plates in pounds. European scales show kilograms. International airlines set baggage limits in one unit and charge overage fees based on the other. Medical charts, nutrition labels, and shipping invoices each pick a system and expect you to keep up.

This guide covers the exact formula, a full table from 1 to 300 lbs, and clear guidance on the situations where getting the number right actually has consequences.

The Formula

To convert pounds to kilograms, multiply by 0.453592:

kg = lbs × 0.453592

To convert kilograms back to pounds, multiply by 2.20462:

lbs = kg × 2.20462

Worked examples:

• 150 lbs × 0.453592 = 68.04 kg
• 200 lbs × 0.453592 = 90.72 kg
• 70 kg × 2.20462 = 154.32 lbs
• 100 kg × 2.20462 = 220.46 lbs

The full exact value is 1 lb = 0.45359237 kg. This was fixed internationally in 1959 under the International Yard and Pound Agreement. It does not vary by country.

Mental Math Shortcut

You will not always have a calculator when you need a quick answer. This two-step trick works well for body weight, gym loads, and luggage estimates:

1. Divide the pounds by 2
2. Subtract 10% of that result

Example: 180 lbs. Half of 180 is 90. Ten percent of 90 is 9. So 90 minus 9 = 81 kg. The exact answer is 81.65 kg. That is less than 1% off.

For the other direction, from kg to lbs: double the kilograms, then add 10%.

Example: 70 kg. Double is 140. Ten percent of 140 is 14. So 140 + 14 = 154 lbs. Exact answer is 154.32 lbs.

Where this breaks down: The shortcut compounds over large numbers. At 300 lbs, the estimate gives 135 kg vs. the exact 136.08 kg, a gap of just over 1 kg. Fine for checking bags. Not fine for weight-based medical dosing or sports weight classes.

Full Lbs to Kg Conversion Table

Pounds (lbs)	Kilograms (kg)	Stone & lb	Grams (g)
1 lb	0.454 kg	0 st 1 lb	453.6 g
2 lbs	0.907 kg	0 st 2 lb	907.2 g
5 lbs	2.268 kg	0 st 5 lb	2,268 g
10 lbs	4.536 kg	0 st 10 lb	4,536 g
15 lbs	6.804 kg	1 st 1 lb	6,804 g
20 lbs	9.072 kg	1 st 6 lb	9,072 g
25 lbs	11.340 kg	1 st 11 lb	11,340 g
30 lbs	13.608 kg	2 st 2 lb	13,608 g
40 lbs	18.144 kg	2 st 12 lb	18,144 g
50 lbs	22.680 kg	3 st 8 lb	22,680 g
60 lbs	27.216 kg	4 st 4 lb	27,216 g
70 lbs	31.751 kg	5 st 0 lb	31,751 g
80 lbs	36.287 kg	5 st 10 lb	36,287 g
90 lbs	40.823 kg	6 st 6 lb	40,823 g
100 lbs	45.359 kg	7 st 2 lb	45,359 g
110 lbs	49.895 kg	7 st 12 lb	49,895 g
120 lbs	54.431 kg	8 st 8 lb	54,431 g
130 lbs	58.967 kg	9 st 4 lb	58,967 g
140 lbs	63.503 kg	10 st 0 lb	63,503 g
150 lbs	68.039 kg	10 st 10 lb	68,039 g
160 lbs	72.575 kg	11 st 6 lb	72,575 g
170 lbs	77.111 kg	12 st 2 lb	77,111 g
175 lbs	79.379 kg	12 st 7 lb	79,379 g
180 lbs	81.647 kg	12 st 12 lb	81,647 g
185 lbs	83.915 kg	13 st 3 lb	83,915 g
190 lbs	86.183 kg	13 st 8 lb	86,183 g
200 lbs	90.718 kg	14 st 4 lb	90,718 g
210 lbs	95.254 kg	15 st 0 lb	95,254 g
220 lbs	99.790 kg	15 st 10 lb	99,790 g
225 lbs	102.058 kg	16 st 1 lb	102,058 g
250 lbs	113.398 kg	17 st 12 lb	113,398 g
275 lbs	124.738 kg	19 st 9 lb	124,738 g
300 lbs	136.078 kg	21 st 6 lb	136,078 g

Body Weight Conversions

Body weight is the most common reason people search for lbs to kg. US scales default to pounds. Fitness apps, BMI calculators, and medical intake forms outside the US ask for kilograms. Here are the most-needed body weight conversions:

Pounds	Kilograms	Stone (UK)
100 lbs	45.4 kg	7 st 2 lb
110 lbs	49.9 kg	7 st 12 lb
120 lbs	54.4 kg	8 st 8 lb
130 lbs	59.0 kg	9 st 4 lb
140 lbs	63.5 kg	10 st 0 lb
150 lbs	68.0 kg	10 st 10 lb
160 lbs	72.6 kg	11 st 6 lb
170 lbs	77.1 kg	12 st 2 lb
180 lbs	81.6 kg	12 st 12 lb
190 lbs	86.2 kg	13 st 8 lb
200 lbs	90.7 kg	14 st 4 lb
210 lbs	95.3 kg	15 st 0 lb
220 lbs	99.8 kg	15 st 10 lb
250 lbs	113.4 kg	17 st 12 lb

BMI uses kilograms and meters. If your scale shows pounds and your height is in feet, convert both before calculating. Feeding pounds and feet into a formula built for kg and meters gives a BMI figure that is roughly 703 times too small.

Where Precision Matters

Medicine and drug dosing

Most drugs are prescribed in milligrams per kilogram of body weight. Get the weight wrong and the dose is wrong. In pediatric care, doses for infants are calculated to tenths of a kilogram, and a rough estimate is not acceptable. The rule in clinical settings: use 0.45359237 for any formal calculation, not the rounded shortcut.

This matters most for weight-sensitive drugs with narrow therapeutic windows, where a small error in one direction under-doses and in the other causes toxicity.

Airline baggage

Most US carriers set the standard checked bag limit at 50 lbs (22.68 kg). Most international carriers set it at 23 kg (50.71 lbs). They are not the same weight. 23 kg gives about 1.4 lbs of extra room compared to 50 lbs. If your scale shows pounds and you are flying an international carrier with a 23 kg limit, 50 lbs puts you safely under. If your carrier lists the limit as 50 lbs and you pack to exactly 23 kg, you are 0.71 lbs over. Small gap, real fee.

Gym training across metric and imperial equipment

A standard Olympic barbell in a metric gym weighs 20 kg (44.09 lbs). In a US gym, the standard bar is 45 lbs (20.41 kg). Close, but not equal. A 3-plate bench in a metric gym is 140 kg (308.6 lbs), not the 315-lb milestone that US plates reach. If you track personal records across both systems, round-number goals in one do not land cleanly in the other.

International shipping

Carriers calculate freight rates using kilograms. A package labeled as 10 lbs, rounded to 5 kg on an invoice, gets billed for 4.536 kg of actual freight plus whatever dimensional weight applies. Overestimating costs money. Underestimating creates customs problems. Use the full conversion factor for any shipment with declared weight.

Nutrition and fitness apps

Calorie and macro calculators need your body weight in the unit they expect. US-built apps often use pounds for input. European apps and research databases default to kilograms. Switch apps or pull data from an international study and a wrong unit entry affects every calculation downstream.

Common Mistakes

Using 0.5 kg per pound instead of 0.4536

Half a kilogram per pound is easy to remember and 10% too high. Convert 150 lbs using 0.5 and you get 75 kg instead of the correct 68 kg. A 7 kg gap matters in medicine, sports weight classes, and shipping declarations.

Reversing the formula

Dividing by 0.453592 instead of multiplying gives wildly wrong answers. Dividing 150 lbs by 0.453592 produces 330 kg. Quick sanity check: 1 kg is heavier than 1 lb, so any weight in kg should be a smaller number than the same weight in lbs.

Rounding the factor to 0.45

Rounding 0.453592 down to 0.45 creates a 0.8% error. At 100 lbs that is 0.36 kg, negligible. At 300 lbs it is 1.1 kg. For drug dosing, weight-class sports, or freight billing, use 0.4536 at minimum.

Treating 50 lbs and 23 kg as identical baggage limits

50 lbs is 22.68 kg. 23 kg is 50.71 lbs. Airlines set limits in one specific unit. Convert from that unit to yours before you pack, not after you arrive at the check-in desk.

Using the wrong formula in spreadsheets

Excel’s CONVERT function uses “lbm” for pounds, not “lb”. The correct formula is =CONVERT(A1,”lbm”,”kg”). Entering “lb” returns an error. The weight value is identical; it is just Excel’s label for the unit.

Avoirdupois vs Troy Pounds

Two types of pound are still in everyday use. Almost every situation uses the avoirdupois pound.

Type	Value in kg	Used for
Avoirdupois pound	0.45359237 kg	Body weight, food, shipping, general commerce
Troy pound	0.37324172 kg	Precious metals (gold, silver, platinum)

The troy pound is 80.5 grams lighter than the avoirdupois pound. When a gold dealer quotes a price per pound, they mean troy. When your bathroom scale shows pounds, it means avoirdupois. Applying the standard 0.453592 conversion factor to a troy pound gives the wrong answer.

Frequently Asked Questions

How many kg is 1 lb?

1 pound equals exactly 0.45359237 kg. For everyday use, 0.4536 is close enough. For medical dosing or scientific calculations, use the full figure.

How do I convert lbs to kg?

Multiply the pounds by 0.453592. Example: 150 lbs × 0.453592 = 68.04 kg. To convert kg back to lbs, multiply by 2.20462.

How many lbs is 1 kg?

1 kilogram equals 2.20462 pounds. A mental shortcut of 2.2 lbs per kg is accurate to within 0.2%, which is fine for most everyday situations.

What is 100 lbs in kg?

100 pounds equals 45.36 kg. Calculated as 100 × 0.453592 = 45.3592 kg.

What is 200 lbs in kg?

200 pounds equals 90.72 kg. Calculated as 200 × 0.453592 = 90.7185 kg.

Is there a quick way to convert lbs to kg in your head?

Divide pounds by 2, then subtract 10% of that result. For 180 lbs: half is 90, minus 9 equals 81 kg. The exact answer is 81.65 kg. Good enough for the gym. Not precise enough for clinical work.

Why does medicine use kilograms instead of pounds?

Drug doses are prescribed as mg per kg of body weight. Kilograms keep the system consistent across countries. A small conversion error can shift a dose outside a safe range, which matters most for pediatric patients and drugs with narrow therapeutic windows.

Are airline baggage limits the same in lbs and kg?

No. 50 lbs equals 22.68 kg. 23 kg equals 50.71 lbs. They look like the same limit but differ by about 0.7 lbs. Convert from your carrier’s listed unit before you pack.

What is the difference between avoirdupois and troy pounds?

The avoirdupois pound (0.45359237 kg) is used for body weight, food, and commerce. The troy pound (0.37324172 kg) is used for precious metals only. They are not interchangeable, and applying the standard conversion factor to a troy pound gives the wrong result.