Calculator
Vitamin D: cost per effective dose
The honest way to compare vitamin D supplements is the cost per 10 micrograms (400 IU), the daily amount the NHS advises adults consider taking, not the price per pack or per capsule. Enter any product's price, pack size and per-serving dose below for an instant cost per effective dose. Information only, not medical advice.
How the calculation works
We convert the label dose to micrograms (1 mcg = 40 IU), divide the pack price by the number of servings to get the cost per serving, then scale that to the NHS reference amount of 10 micrograms a day. The result is a single like-for-like number, pence per 10 mcg, that works across every pack size and strength. We also show what one serving a day costs across the roughly 182 days of October to March, the period the NHS advice focuses on, and flag any serving above the NHS 100 microgram daily upper guidance.
Reference figures: 10 mcg (400 IU) daily advice and 100 mcg upper guidance from NHS, Vitamin D, as of 2026-06-11.
Information only, not medical advice. This tool is educational and is not a substitute for a registered clinician. It does not diagnose anything and does not recommend that you take any supplement. Always read product labels and speak to your GP or pharmacist before starting, stopping or combining supplements.
Read more
See how much vitamin D you really need, our vitamin D guide and the best vitamin D supplements UK roundup. More calculators are on the cost per effective dose hub.
Frequently asked questions
What counts as an effective dose of vitamin D?
We anchor to the NHS advice that adults consider a daily supplement containing 10 micrograms (400 IU) of vitamin D, particularly in autumn and winter. The calculator prices every product against that same 10 microgram reference so you can compare them like for like. Your own needs may differ; ask your GP or pharmacist.
Is a higher-dose vitamin D product better value?
Often per microgram it is, but more is not automatically better. The NHS advises adults not to take more than 100 micrograms (4,000 IU) a day unless a clinician recommends it. The calculator flags any product whose per-serving dose exceeds that figure.
How do I convert IU to micrograms?
Divide by 40. A 1000 IU capsule contains 25 micrograms; a 400 IU capsule contains 10 micrograms, the routine NHS amount. The calculator accepts either unit and shows both.
Why price per 10 micrograms rather than per capsule?
Because capsule doses vary enormously, from 10 to 100 micrograms, a per-capsule price tells you nothing. Pricing per 10 micrograms (the NHS reference amount) puts every product on the same scale, which is the comparison sellers rarely show.
Editor, Her Vitals
Oliver leads Her Vitals's editorial coverage of women's life-stage health and supplements. He curates and reviews existing branded products across trying to conceive, pregnancy, postnatal, perimenopause, menopause and the senior years, weighing what the evidence supports against guidance from bodies such as EFSA, the NHS and NICE, and is clear that the content is information rather than medical advice.
Last reviewed: 11 June 2026