DoseDrill

Calculators · Oral liquid

Free calculator

Oral liquid dose calculator

Enter the ordered dose and the concentration on the bottle label. See the desired-over-have formula for the method.

Example: a bottle labeled 250 mg per 5 mL is strength 250 and per volume 5.

Volume to give

10 mL
1. Identify what you have and what you want
Have: 250 mg per 5 mL · Want: 500 mg
2. Set up dimensional analysis so mg cancels
500 mg × ( 5 mL ÷ 250 mg )
3. Cancel mg and solve
= ( 500 × 5 ) ÷ 250 mL
= 10 mL

How it works

Oral liquids use the desired-over-have rule. The label tells you how many mg are in a known volume; the ordered dose scales that volume:

Volume (mL) = ( ordered dose ÷ label strength ) × label volume

The full method, with practice problems, is in the oral liquid dose lesson.

Worked example

The prescriber orders 500 mg of amoxicillin oral suspension. The bottle is labeled 250 mg per 5 mL. How many milliliters should the nurse give?

Answer: 10 mL
1. Identify what you have and what you want
Have: 250 mg per 5 mL · Want: 500 mg
2. Set up dimensional analysis so mg cancels
500 mg × ( 5 mL ÷ 250 mg )
3. Cancel mg and solve
= ( 500 × 5 ) ÷ 250 mL
= 10 mL

Frequently asked questions

What is the oral liquid dose formula?

Desired over Have times Quantity: divide the ordered dose by the label strength, then multiply by the volume that carries it. For example, 500 mg ordered with a 250 mg per 5 mL label is (500 / 250) x 5 = 10 mL.

Why is the answer rounded to tenths of a milliliter?

Oral syringes are marked in 0.1 mL increments, so liquid doses are rounded to one decimal place.

What should be used to measure an oral liquid dose?

Use an oral syringe or a calibrated dosing cup, never a household spoon. Household spoons vary too much to measure medication safely.