Calculations

Question 1

What is a 1% solution or mixture?

Answer 1

1g in 100ml or
1g in 100mg or
1ml in 100ml

e.g. 0.9% saline = 0.9g in 100ml = 9g in 1L

Question 2

What does 1 in 1000 mean?

Answer 2

1g in 1000ml

0.1%

Question 3

What does 1 part per million mean?

Answer 3

1g in 1,000,000ml. = 1mg in 1 L

Question 4

What does 1 in 10,000 mean?

Answer 4

1g in 10,000ml

0.01%

Question 5

You need a dose of Zmg
You have a mg/ml solution

How much do you need to give?

Answer 5

Zmg (weight you want) / mg in the solution (weight you have) * volume it’s in

E.g.
Dose is 100mg
Solution is 50mg/ml
Volume needed = 100/50*1 = 2ml

Question 6

How many mg/ml in a Y% solution?

Answer 6

10Y

multiply % by 10 to give mg/ml

Question 7

What percentage is a solution of Xmg/ml?

Answer 7

X/10

divide mg/ml by 10 to give percentage

Question 8

How many millimoles are there in Xml of a Ymg/ml solution?

Answer 8

Y (mg/ml) / molecular mass * X (ml)

E.g.
Millimoles of Na in 500ml of 1.8mg/ml NaCl
Molecular mass NaCl = 58.5

1.8 / 58.5 * 500 = 15mmol

Question 9

How many millimoles of X are there in a Y% solution?

Answer 9

Y% / molecular mass * 10 * volume (ml)

E.g.
Millimoles of NaCl in 1L of 0.9% NaCl
Molecular mass of NaCl = 58.5

0.9 / 58.5 * 10 * 1000 = 154mmol