Nursing math workspace
Nursing Dosage Calculator
Check tablets, liquid volumes and weight-based amounts from a practice problem. Choose the units, see each calculation, and compare the working with your own.
Free study tool · Last reviewed November 3, 2026
Choose a calculation
Each tab starts with an unnamed math example. Replace its values with those from your practice question.
Match the order to the supply
7.5 mL
Both amounts are already in mg.
(240 mg ÷ 160 mg) × 5 mL = 7.5 mL.
The mass units cancel. The remaining unit is mL.
Arithmetic is shown to at most 12 significant digits. This is display precision, not a dose-rounding instruction. Follow the rounding requested in your practice problem.
For study only. Not for clinical use.
Set up the problem
Three details decide the calculation
Before typing numbers, identify the amount requested, the way the supply is expressed, and the unit your answer needs. A correct division with the wrong units still answers the wrong question.
- 01
Find the requested amount
For a tablet or liquid problem, D is the ordered amount. Read its unit: 0.375 g and 375 mg describe the same mass. A daily total is different from the amount in one dose.
- 02
Keep the label together
H and Q form a pair. A label of 160 mg in 5 mL means that all 5 mL contains 160 mg. Entering 1 mL as Q would change the concentration and the answer.
- 03
Name the answer unit
A liquid question asks for mL; a tablet question asks for tablets. A weight calculation here gives mg per dose. Match that result to the question before considering rounding.
This setup follows the unit-cancellation methods in Open RN’s tablet dosage, liquid concentrations and weight-based calculations chapters (ACC adaptation, CC BY 4.0). The practice numbers on this page are original arithmetic examples, not product strengths or treatment instructions.
Check your working
Follow the units through the answer
Work each example on paper first. Then load the corresponding calculator tab and compare the conversion, setup and result.
Liquid volume
Practice order: 240 mg. Supply: 160 mg in 5 mL. Both amounts are in mg, so no mass conversion is needed.
(240 mg ÷ 160 mg) × 5 mL = 7.5 mL.
Check the scale: 240 mg is one and a half times 160 mg, so the answer should be one and a half times 5 mL.
Tablets with a conversion
Practice order: 0.375 g. Supply: 125 mg in each tablet. Convert 0.375 g to 375 mg first.
(375 mg ÷ 125 mg) × 1 tablet = 3 tablets.
Check by reversing the calculation: 3 × 125 mg = 375 mg. Entering 0.375 as mg would produce a different answer.
A daily weight-based amount
Practice order: 16 mg/kg/day in 3 equal doses. Practice weight: 27 kg. Find the daily total before dividing it.
16 × 27 = 432 mg/day. Then 432 ÷ 3 = 144 mg/dose.
If the order instead said 16 mg/kg/dose, 432 mg would already be the amount per dose. Do not divide it again.
Conversion check
Mass and volume are different units
The calculator converts between grams, milligrams and micrograms. It cannot turn mg into mL without the concentration from the practice problem.
| Starting unit | Convert to | Operation |
|---|---|---|
| g | mg | Multiply by 1,000 |
| mg | mcg | Multiply by 1,000 |
| mcg | mg | Divide by 1,000 |
| mg | g | Divide by 1,000 |
These relationships follow the milli and micro prefixes in NIST’s metric prefix reference. The calculator spells micrograms as “mcg” in its controls. In the weight tab, enter the weight in kilograms; that tab does not convert pounds.
A concentration needs both parts
Understand the result
Check arithmetic before deciding how to round
The result panel keeps up to 12 significant digits for readability. It does not choose a rounding rule for medication administration.
- Use the rounding instruction printed in your practice problem. Keep intermediate arithmetic until the final step unless that problem explicitly directs otherwise.
- A fractional tablet result is an arithmetic answer, not proof that the product can be divided. This tool does not round tablets or evaluate a dosage form.
- A zero, negative number, blank field or invalid divisor produces no result. Check for an omitted value or a unit typed into a number field.
- A result alone does not establish a safe dose. This calculator has no drug reference, patient assessment, maximum-dose limit or administration guidance.
Open RN’s rounding guidance distinguishes the final answer from intermediate arithmetic and emphasizes the relevant policy. It also describes using a leading zero for a decimal below one. This tool shows 0.375, for example, rather than .375.
Use what you learned
Move from checking an answer to solving one
Choose the next exercise by the step you found hardest. These pages contain questions and explanations; the calculator is here when you want to check your setup.