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NMC CBT Drug Calculations: Part A Formulas, Worked Examples and the Two-Minute Rule

Writer: Media Team
Media Team
6 days ago
4 min read

NMC CBT drug calculations are where many nurses lose the exam, because Part A is short, strict and unforgiving of small errors. The good news is that NMC CBT drug calculations follow a small set of patterns you can learn. This guide covers the Part A format, question types, key formulas with worked examples, and a routine to stay within two minutes per question. For structured support, see our CBT training.

Quick answer (updated October 2026): Part A of the NMC CBT has 15 questions in 30 minutes. The NMC CBT pass mark for Part A is 13 out of 15 (87%), as set out in the NMC test specification. Practise daily and aim to complete each question in under two minutes.

Nurse using an on-screen calculator to answer an NMC CBT drug calculation question in Part A

NMC CBT Part A Format and Pass Mark     

Part A is the numeracy section of the NMC Test of Competence computer-based test. You take it in the same sitting as Part B, but you pass or fail each part separately.

Part A has 15 questions and a 30-minute time limit, which gives you an average of two minutes per question. You need 13 out of 15 correct to pass so you can afford only two errors. If you fail one part, you resit that part only.

Check the NMC CBT pass mark and the question count on the NMC website before you book, because the NMC can update the test. Our guide to the CBT exam format explains how the full test is structured, including Part B.

The Calculation Types Part A Covers    

The NMC test specification lists six types of Part A questions:

  • Measuring the correct dose

  • Metric units

  • Oral medications

  • Injections

  • IV infusions

  • Fluid balance

Most NMC CBT drug calculations combine one of these types with a conversion step, such as grams to milligrams or hours to minutes. For example, an IV infusion rate question often asks you to convert time before you calculate. Each question gives you the figures you need. Your task is to choose the right method and apply it without slips.

Key Formulas With Worked Examples for NMC CBT Drug Calculations    


These drug calculation formulas cover most Part A questions. Learn them until they feel automatic.

  1. Dose from strength and volume: dose required ÷ dose available × volume. Example: 250 mg is prescribed, and the stock is 500 mg in 5 mL. 250 ÷ 500 × 5 = 2.5 mL.

  2. IV infusion rate (mL per hour): volume ÷ time in hours. Example: 1,000 mL over eight hours. 1,000 ÷ 8 = 125 mL per hour.

  3. Drops per minute: volume × drop factor ÷ time in minutes. Example: 1,000 mL over five hours with a drop factor of 15 drops per mL. 1,000 × 15 ÷ 300 = 50 drops per minute.

  4. Weight-based dosing: dose per kg × weight in kg. Example: 15 mg per kg for a child weighing 12 kg. 15 × 12 = 180 mg.

Always read the units in the question first. In practice, check every dose against the BNF.

Beating the Two-Minute Limit    

Thirty minutes for 15 questions means two minutes each. If your method is sound, you'll save time, so build speed in three steps.

  1. Practise daily. Do five to ten questions a day, one type at a time, until the drug calculation formulas are automatic. Give extra time to IV infusion rate questions, because converting hours to minutes is an easy place to slip.

  2. Check units first. Convert micrograms, milligrams, grams and hours before you calculate, and write the unit beside your answer if asked

  3. Sit a weekly NMC CBT mock test. Take 15 questions in 30 minutes. Note which question types take the longest, then review every error before your next NMC CBT mock test. Repeating a timed NMC CBT mock test makes the real timing feel familiar.

Our 30-day study plan shows how to fit numeracy practice around Part B revision.

FAQ    

How many drug calculation questions are in the NMC CBT? Part A has 15 numeracy questions, which you must complete in 30 minutes. Part B, the clinical section, has 100 questions. Check the NMC website for current figures before you book your test.

What is the Part A pass mark? The NMC CBT pass mark for Part A is 13 out of 15 (87%). You pass or fail Parts A and B separately, so you resit only the part you fail.

Can I use a calculator? Part A provides an on-screen calculator for calculation ques

tions. Confirm the current calculator rules in the NMC CBT information booklet before your test date, as the rules may change.

Conclusion    

NMC CBT drug calculations reward steady practice more than natural talent. Learn the formulas, check your units and time yourself with a weekly NMC CBT mock test until two minutes per question feels routine. Once you have cleared the CBT, our OSCE training prepares you for the practical stage of the NMC Test of Competence. Join CBT training.Disclaimer

This article is for general guidance only and reflects the NMC CBT structure and numeracy requirements as publicly stated at the time of writing (October 2026). Pass marks, question formats and calculator rules can change. Always verify the latest information on the NMC website and in the official CBT information booklet before booking or sitting the exam.

 
 
 

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