Infusions — drug calculations
Infusion rate: how to calculate mL per hour
The infusion rate formula with examples, a calculator and how to calculate when the dose is given per kg per minute.
The infusion rate formula
The rate is the volume divided by the time.
If the time is given in minutes, first convert it to hours by dividing by 60. If you want to work in drops rather than use a pump, see the drip rate calculator.
Calculate the infusion rate
Enter the volume and the time.
Calculate mL per hour
Infusions with a drug in the solution
When the prescription is given as an amount of drug per unit of time, you need the strength of the solution.
Dose per kg per minute
Some prescriptions are written as micrograms per kg per minute. First work out the dose per hour, then the rate.
5 × 70 × 60 = 21,000 micrograms per hour
21,000 ÷ 1000 = 21 mL/hour
Frequently asked questions
How do you calculate mL per hour?+
Divide the volume in mL by the time in hours. 500 mL over 4 hours gives 125 mL/hour.
What do I do if the time is in minutes?+
Divide the minutes by 60 to get hours before you calculate.
How do I calculate when the dose is given per kg per minute?+
Multiply the dose by the weight and by 60 to get the dose per hour, then divide by the concentration of the solution.
How is this different from drip rate calculations?+
Drip rate gives drops per minute for a gravity drip. A pump is set in mL per hour.
Practise infusion calculations
Practise mL/h, pump settings and infusions with a drug in the solution. Dos is a practice app for drug calculations, with practice tests of ten questions, a built-in calculator next to each question and statistics per topic.
