HESI A2 Math Formulas & Conversions Cheat Sheet

The HESI A2 Math section gives you 50 questions in 50 minutes. You'll need to work fast and accurately. Here's every formula and conversion you need to memorize.

Section Overview

The HESI A2 Math section tests basic arithmetic, fractions, decimals, ratios, proportions, percentages, and measurement conversions. There is no advanced algebra or calculus. However, the tight time limit (1 minute per question) means you must have these formulas memorized — not calculated from scratch.

🔢 Fractions & Decimals

📐 Ratios & Proportions

This is the exact format you'll see on nursing dosage questions. Practice until it's automatic.

💯 Percentages

⚖️ Metric Conversions (MUST MEMORIZE)

Metric conversions make up a huge portion of the HESI math section. Commit this table to memory:

Pro tip: To convert within the metric system, remember King Henry Died By Drinking Chocolate Milk — Kilo, Hecto, Deka, Base, Deci, Centi, Milli. Moving right means multiply by 10; moving left means divide by 10.

Download the printable one-page cheat sheet with all these conversions →

🔤 Order of Operations (PEMDAS)

🏥 Dosage Calculation Formula

This is the most nursing-relevant formula on the exam. You will absolutely see at least 2–3 questions using it:

Example: The doctor orders 500 mg. The available tablets are 250 mg each.
500 / 250 × 1 tablet = 2 tablets

5 Time-Saving Tips for Test Day

1. Estimate first — before calculating, estimate the answer to eliminate obviously wrong choices.
2. Convert fractions to decimals when comparing or adding — it's usually faster.
3. Cross-multiply immediately whenever you see a proportion problem.
4. Memorize the conversions table above — at least 5–8 questions will test these directly.
5. Practice with a timer — take our free HESI A2 practice quiz to build speed under pressure.

Roman Numerals (Yes, They're on the HESI)

Many students are surprised to find Roman numeral questions on the HESI A2. Healthcare prescriptions sometimes use them, so you need to know the basics:

Rounding Rules

You'll encounter rounding in multiple contexts — dosage calculations, statistical questions, and unit conversions. Remember these rules:

• 5 or greater — round up. Example: 3.456 rounded to one decimal = 3.5
• 4 or less — round down. Example: 3.432 rounded to one decimal = 3.4
• Whole number rounding: 1,847 rounded to the nearest hundred = 1,800
• In dosage context: Always follow the rounding instruction in the question. If it says "round to the nearest tenth," do exactly that — no more, no less.

Word Problems: The HESI Format

Nearly half of HESI A2 Math questions are word problems. They test whether you can extract the math from a real-world scenario. Here's a reliable 4-step approach:

1. Read the entire problem first. Don't start calculating until you understand what's being asked.
2. Identify what's given and what's wanted. Write down the numbers and their units.
3. Set up the equation. If it's a proportion, cross-multiply. If it's a percentage, use the percentage formula.
4. Solve and check units. If the question asks for milligrams, your answer must be in milligrams — not grams.

Example word problem: "A patient needs to take 750 mL of fluid over 6 hours. How many mL per hour should the patient drink?"

Least Common Multiple (LCM) and Greatest Common Factor (GCF)

These appear frequently when adding fractions or simplifying answers:

Common Mistakes to Avoid

These are the errors our HESI tutors see students make most frequently during practice sessions:

• Forgetting to simplify fractions. If your answer is 6/8, reduce it to 3/4. The HESI answer choices will always use simplified fractions.
• Mixing up metric direction. Kilo to milli is multiply by 1,000,000 — not divide. Use the King Henry mnemonic every time.
• Misreading the question. "How many MORE tablets" is different from "How many tablets TOTAL." Read carefully.
• Not converting units before calculating. If the question gives you kilograms but asks for grams, convert first, then calculate.
• Rounding too early. Keep full decimal precision throughout your calculation and only round at the final step.

Frequently Asked Questions

How many math questions are on the HESI A2?

The HESI A2 Math section has 50 questions with a 50-minute time limit, giving you exactly 1 minute per question. All questions are multiple choice with 4 answer options.

Can I use a calculator on the HESI A2 Math section?

No. Calculators are not allowed on the HESI A2 Math section. You must do all calculations by hand, which is why memorizing the formulas and conversions is critical. You will be provided with scratch paper.

What math score do I need for nursing school?

Most nursing programs require a minimum HESI A2 composite score of 75-80%, though competitive programs want 85%+. Some schools set minimum section scores — often 75% for Math specifically. Check your target school's requirements.

Is the HESI A2 Math section harder than the TEAS Math?

The HESI A2 Math focuses more heavily on basic arithmetic, fractions, and unit conversions. The TEAS 7 Math includes some algebra and data interpretation. Most students find the HESI math slightly easier in content but harder in time pressure since you get less time per question.

What topics are NOT on the HESI A2 Math section?

You will not see algebra, geometry, trigonometry, calculus, statistics, or probability on the HESI A2 Math section. It focuses exclusively on basic math: fractions, decimals, ratios, proportions, percentages, and measurement conversions.

How should I study for HESI A2 Math if I'm bad at math?

Start with the basics: make sure you can add, subtract, multiply, and divide fractions without a calculator. Then memorize the metric conversion table. Practice 10-15 problems per day with a 1-minute timer per question. Our HESI tutors specialize in helping students who struggle with math — book a free consultation to get a personalized study plan.