Timing — drug calculations
Daily dose and timing calculations
How to calculate with daily doses, number of administrations and clock times, with a table and worked examples.
Daily dose and number of administrations
Read how the prescription is written: per administration or per day.
| Prescription | Means |
|---|---|
| 1 × 1 | once a day |
| 1 × 3 | three times a day |
| Every 8 hours | 3 times a day |
| Every 6 hours | 4 times a day |
| Every 12 hours | 2 times a day |
600 ÷ 3 = 200 mg per administration
15 × 20 = 300 mg/day. 300 ÷ 3 = 100 mg per administration
Clock times and infusion time
Calculate the hours and minutes separately.
14:30 + 3 h = 17:30. 17:30 + 45 min = 18:15
Convert to minutes
Convert hours to minutes by multiplying by 60 if you need the same unit.
Use the 24-hour clock
That way you cannot confuse morning and afternoon.
Check for passing midnight
If the time goes past 24:00, subtract 24 hours.
Need the rate? See the infusion rate calculator and the drip rate calculator.
Frequently asked questions
What does 1 × 3 mean?+
Three times a day.
How many administrations is every 8 hours?+
24 ÷ 8 = 3 administrations a day.
How do you calculate the dose per administration?+
Divide the daily dose by the number of administrations per day.
How do I work out the finish time of an infusion?+
Add the hours and minutes separately to the start time, preferably using the 24-hour clock.
Practise daily doses and timing
Practise daily doses, administrations and infusion time in practice questions, with the calculator next to each question. 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.
