A twenty per cent lower risk of what, exactly?

Reports on health, healthcare and adult education — and a calculator that turns the percentage in a health headline back into the number of people it describes. These are summaries of what was published. Nothing here is advice about your own health.

Open the risk calculator → Read the guides

Health & medicine

View all →

Healthcare & policy

View all →

Adult education

View all →

Free · runs in your browser

What the percentage means

Health headlines report the relative change and almost never the absolute one. Put in the baseline risk and the percentage a study reported, and this returns the two numbers that actually describe it: how many people in a thousand, and how many would have to be treated for one of them to benefit.

Open the risk calculator →
  • Relative change turned into people per thousand
  • The absolute difference, in percentage points
  • Number needed to treat, or to harm
  • Runs in your browser — nothing is sent or stored

Corrections

Has a result here been superseded?

Health reporting ages badly and dangerously: guidance changes, a trial fails to replicate, a drug is withdrawn. If you know that has happened to something on this site, tell us and we will note it on the article.

Email the editors

[email protected]

Most messages are answered within a few working days. We cannot answer questions about your own health.