Common Registration Assessment, Part 1
Age-band doses from a provided table
Practise reading a dose from a supplied age table and turning it into a volume, with three original worked questions.
Published 9 October 2026. Independent revision material, not GPhC questions, not for patient care.
Some questions give a table of doses by age band and ask you to pick the right row before any arithmetic. The skill is reading the table exactly as printed, including whether a band says "to under" or "up to and including".
The tables here are fictional and exist only to practise the method. Read the band first, apply the rule in that row, then convert to a volume or number of doses.
The method
- Find the patient age or weight and match it to one row of the table.
- Note whether the row gives a dose, a dose per kg, or a daily total.
- Apply any per-kg or per-day instruction in the row.
- Convert the dose to a volume using the strength given.
- Check the answer against the unit the question asks for.
Three practice questions
Work each one on paper first, then open the answer. All drugs and patients are fictional.
Question 1
A fictional table gives 2.5 mL for ages 1 to under 6 years, 5 mL for 6 to under 12 years and 10 mL for 12 to under 18 years. A child is exactly 6 years old. What volume is given?
Show the answer
Answer: 5 mL
Working: Age 6 years falls in the 6 to under 12 row, not the 1 to under 6 row. The dose is 5 mL.
Question 2
A fictional table gives 12.5 mg/kg per dose for children under 5 years. A child aged 4 years weighs 16 kg. The syrup is 125 mg in 5 mL. What volume is one dose?
Show the answer
Answer: 8 mL
Working: Dose = 12.5 × 16 = 200 mg. Volume = 200 ÷ 125 × 5 = 8 mL.
Question 3
A fictional table gives 30 mg/kg per day in three equal doses for ages 5 to under 12. A child aged 8 weighs 30 kg. How many mg are in each dose?
Show the answer
Answer: 300 mg
Working: Daily total = 30 × 30 = 900 mg. Each dose = 900 ÷ 3 = 300 mg.
Highlight the row
Underline the row you used and write its rule beside your working. It shows where each number came from and stops you mixing two rows.
Where marks are lost
- Choosing the row above or below at a boundary age.
- Using a per-day amount as a per-dose amount.
- Applying the weight rule to a row that gives a fixed dose.
Frequently asked questions
What does "to under 6 years" mean?
It covers ages up to the day before the sixth birthday. A child aged exactly 6 belongs in the next row.
Should I use age or weight?
Use whichever the table row uses. If the row gives mg/kg, weight matters; if it gives a fixed volume, age decides.
Sources
- The Pharmaceutical Journal, medication maths: using provided formula
- The Pharmaceutical Journal, preparing for the GPhC pharmaceutical calculations assessment
- GPhC, 2026 assessment specification and permitted items
The questions above are original and use fictional drugs. PreRegExamPrep is not affiliated with or endorsed by the General Pharmaceutical Council.
Practise until the method is automatic
Try 15 free questions with worked answers. No sign-up required.
More calculation topics
- Dose by weight calculations for the GPhC assessment
- Volume to give: liquid medicine calculations
- Percentage strength calculations: w/v, w/w and ratios
- Dilution calculations with C1V1 = C2V2
- Infusion rate calculations in mL per hour
- Drip rate calculations: drops per minute
- Body surface area calculations
- Creatinine clearance (Cockcroft-Gault) calculations
- Moles and millimoles calculations
- Displacement volume calculations for reconstitution
- Quantity to supply calculations
- Using a provided formula in calculations
- Dose information from packaging and labels
- Diluting a stock to a lower strength
- Medicine cost and switch calculations
- Rounding rules in calculations
- Enteral feed rate calculations
- Electrolyte content over time
- Infusion dose per kg per hour
- Rounding doses to measurable volumes
- Relative risk and relative risk reduction
- Absolute risk reduction and number needed to treat
- Odds ratio and confidence intervals
- Relative versus absolute risk reduction
- Loading dose and volume of distribution
- Top-up doses from measured drug levels
- Salt correction factors
- Mass and molar drug concentrations
- Half-life and falling drug levels
- Steady-state concentration and infusion rate
- Bioavailability and equivalent oral doses
- Oral maintenance dose and dosing interval
- Elimination rate constant and half-life
- Accumulation towards steady state
- Ratio strengths and one in X
- Serial dilution factors
- Mixing solutions of different strengths
- Tablet quantities for reducing regimens
- Equivalent doses from provided conversion tables
- Thresholds and dose-banding algorithms
- Unit conversions for mass and volume
- Units and units per mL
- Reconstituting powders and final concentration
- Millimoles and milliequivalents
- Infusion time and volume remaining
- Days supply from pack sizes
- Percentage w/v and w/w conversions
- Ideal and adjusted body weight from formulae
- Diluting creams and ointments by weight
- Scaling a formula to a batch size
- Tablet fractions and split doses
- Stones, pounds, inches and metric conversions
- Micrograms per minute from mg per hour
- Percentage change and mark-up
- Molar solutions and mass per volume
- Osmolarity from component concentrations
- Direct proportion and cross-multiplication
- Scientific notation and very small quantities
- Stock use and reorder quantities
See also the formula sheet, the eight sample questions and the approved calculator page.