TEAS Dosage Calculations & Ratios: Step-by-Step Practice Guide

Dosage calculation questions on the TEAS Math section test your ability to use ratios and proportions to determine how much of a medication to administer — a skill that previews the math you'll use throughout nursing school. These questions sit within the Measurement & Data content area of the 38-question Math section, and while they're a smaller slice of the exam than general algebra, nursing programs pay close attention to how well applicants handle them, since dosage errors have real clinical consequences.

Build this skill with TEAS Math practice questions that include step-by-step rationales.

The Core Formula

Most TEAS dosage problems reduce to one relationship:

Desired dose ÷ Available dose × Quantity = Amount to administer

Or, written as a proportion:

Desired dose / Available dose = Amount to administer / Quantity

You then cross-multiply and solve for the unknown.

Worked Example 1: Basic Dosage Calculation

A provider orders 500 mg of a medication. The medication is available as 250 mg per 5 mL. How many mL should be administered?

1. Set up the proportion: 500 mg / 250 mg = x mL / 5 mL
2. Cross-multiply: 500 × 5 = 250 × x → 2,500 = 250x
3. Solve: x = 2,500 ÷ 250 = 10 mL

Worked Example 2: Weight-Based Dosage

A medication is ordered at 5 mg per kg of body weight. The patient weighs 70 kg. How many mg should be administered?

1. Multiply the dose per kg by the patient's weight: 5 mg × 70 = 350 mg

Weight-based problems are just multiplication once you identify the correct rate — the challenge is reading the problem carefully enough to pull out the right numbers.

Worked Example 3: Metric Conversion Within a Dosage Problem

An order calls for 0.5 g of a medication. It's available as 250 mg tablets. How many tablets should be given?

1. Convert grams to milligrams: 0.5 g × 1,000 = 500 mg
2. Divide by the tablet strength: 500 mg ÷ 250 mg = 2 tablets

This is why metric conversions and dosage calculations are taught together — most real dosage problems require a unit conversion before you can even set up the ratio.

Common Mistakes to Avoid

• Skipping unit conversion. If the order and the available medication are in different units (g vs. mg, mcg vs. mg), convert first — this is the single most common source of errors.
• Cross-multiplying incorrectly. Always double-check which numbers are diagonal from each other in your proportion before multiplying.
• Losing track of what the question is asking. Some problems ask for mL, others for tablets, others for mg — reread the question after you calculate to confirm your answer is in the right unit.
• Rushing because the calculator "should" handle it. The TEAS calculator is basic four-function only — it won't do unit conversions or proportions for you, so the setup has to be correct going in.

Study Strategy

1. Master the proportion formula cold — desired/available × quantity is the backbone of nearly every dosage question.
2. Drill metric conversions separately until they're automatic (mg↔g, mcg↔mg, mL↔L), since most errors happen at the conversion step, not the math step.
3. Practice weight-based and rate-based problems, not just simple tablet/liquid conversions — these show up in slightly more complex forms.
4. Time yourself. With about 90 seconds per Math question, you need to set up a dosage proportion quickly and accurately. TEAS Academy's Math practice test includes ratio, proportion, and dosage-style questions with instant explanations so you can check your setup, not just your final answer.