Lessons · Nursing · kilograms from pounds
Kilograms from pounds: divide by 2.2
One kilogram is 2.2 pounds. Pounds to kilograms is a division by 2.2; kilograms to pounds is a multiplication.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
A weight-based order says mg per kg, and the scale in the clinic, or the parent at the bedside, says pounds. The conversion happens before any dose is worked out, and it happens on paper, not in your head.
How to think about it
Write the weight with its unit. If it says lb, divide by 2.2 and write kg on the result. Check the direction: the number in kilograms is always smaller than the number in pounds, a little under half.
Worked example
1 kg = 2.2 lbThe one fact. Every weight conversion on the floor is this line, one way or the other.
154 lb / 2.2 = 70 kgPounds to kilograms: divide. Seventy is a little under half of 154, which is how it should look.
22 lb / 2.2 = 10 kgA small child. The same division.
60 kg × 2.2 = 132 lbThe other way, when a chart in kilograms has to be said to someone who thinks in pounds.
Your turn
A patient weighs 110 lb. Write the line that gives the weight in kilograms.
110 / 2.2 = kg
Solve one, graded on the server
The trap
Multiplying instead of dividing. 154 lb × 2.2 is 338.8, and a weight-based dose worked from that is more than four times too large. If the kilograms came out bigger than the pounds, the arithmetic went the wrong way.