Injection Pen Dose Calculator
Convert between a dose and the number of dial 'clicks' on an injection pen, using numbers you read off your own pen and prescription. It's a plain arithmetic helper — it names no medication, has no drug presets, and gives no dosing advice. Not medical advice: always follow your prescriber and the manufacturer's instructions.
Not medical advice — a maths tool only. This converts between a dose and dial “clicks” using numbers you enter from your own pen. It is a rounded estimate, names no medication, and is not a dosing recommendation. Always follow your prescriber and the manufacturer’s instructions, and never use it to change a prescription dose. Splitting a pen into partial doses can be inaccurate — check with your pharmacist or prescriber.
Your pen
Read these two numbers off your own pen and prescription.
That’s 0.25 mg per click (4 clicks per mg).
For a 5 mg dose
20 clicks
Exact: 20 clicks. At 20 clicks the pen delivers about 5 mg.
Estimates are simple arithmetic (dose ÷ strength-per-click). They are not a dosing recommendation and do not account for how any specific pen or medicine is designed to be used. This tool does not support, and will never provide dosing for, unapproved or illegally-obtained substances. Confirm anything before you act with your prescriber or pharmacist.
Before you rely on this: Safety-critical: treat this as a preliminary check only. Always verify against the governing standards and have a competent person review the result before use.
How to use this calculator
- Read two numbers off your own pen and script: how many clicks make a full dose, and the strength of that full dose (with its unit).
- Choose what to work out: the clicks needed for a target dose, or the dose delivered by a number of clicks.
- Enter your target dose (or number of clicks) and read the estimate, which updates as you type.
- Check the rounding and over-a-full-dose notes, then confirm the result with your prescriber or pharmacist before acting.
- Use Copy result to save the figures — the estimate and the not-medical-advice note are copied together.
How it works
The maths is deliberately simple. It works out the strength delivered per click as the full-dose strength divided by the clicks for a full dose. Clicks for a target dose = target ÷ strength-per-click; dose from clicks = clicks × strength-per-click. Because pens click in whole steps, the clicks are rounded and the tool shows the actual dose that the rounded number delivers.
It is a neutral converter, not a dosing tool. It contains no medication names, no built-in strengths and no recommendations — every number comes from you. It also flags when a request exceeds a single full dose for the pen details you entered, so an obvious slip is easy to catch. It does not model how any particular pen or medicine is designed to be used.
Tips
- Round with care: if the rounded clicks change the dose, check whether the step up or down is acceptable with your prescriber.
- Double-check the unit (mg, mcg, units or mL) matches how your pen and script are written before you trust a number.
Frequently asked questions
Is this medical advice?
No. It is a maths tool that converts between a dose and dial clicks using numbers you enter. It is not a dosing recommendation, it names no medication, and it should never be used to change a prescription dose. Always follow your prescriber and the manufacturer's instructions.
Why doesn't it list specific medications or pens?
Deliberately. Dosing depends on the exact product, strength and clinical situation, so building in medication-specific numbers would be unsafe and misleading. Instead you enter your own pen's figures, and the tool just does the arithmetic.
Are partial or 'split' doses accurate?
Not necessarily. Many pens are designed for set doses, and dialling partial amounts by counting clicks can be imprecise and isn't always how the device is meant to be used. Treat the result as a rough estimate and confirm it with your pharmacist or prescriber.
Is my information private?
Yes. There is no sign-up and nothing is uploaded — the calculation runs entirely in your browser, so the numbers you enter never leave your device.
Does it work for unapproved or black-market substances?
No. This tool is a general unit converter for legitimately prescribed medicines used as directed. It does not support, and will never provide dosing for, unapproved or illegally-obtained substances.
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Cite this tool
Zerdly. (2026). Injection Pen Dose Calculator. Retrieved from https://www.zerdly.com/tools/injection-pen-dose-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.