Every morning involves risk. Brewing coffee. Crossing the road. Commuting to work. Each activity carries a measurable probability of death.@cr-mundane
A micromort (mm) is a one-in-a-million chance of death from a single activity.
All of these are below 1 mm — risks so small we never perceive them as dangerous.
The 12x ratio between a 30-minute bicycle commute and a cup of coffee sounds alarming, but in absolute terms it is the difference between a 0.01 and 0.12 in a million chance. Both are negligible.
Hover over the bars to compare.
Now zoom out. Hover over any dot to see the activity name and micromort value.@cr-spectrum
The micromort scale spans six orders of magnitude — from a dental X-ray (0.05 mm) to summiting Everest (~38,000 mm).
Bottom (< 1 mm): daily activities — commuting, coffee, office work, dental X-rays. Risks so small we never notice them.
Middle (1–100 mm): risks we weigh consciously — a night in hospital (75 mm), general anaesthesia (10 mm), a long-haul flight (4 mm), running a marathon (7 mm).
Top (> 100 mm): risks that make headlines — base jumping (430 mm per jump), Himalayan mountaineering (12,000 mm), Everest at ~38,000 mm — roughly a 4% chance of death per ascent.
Not all risks kill in an instant.@cr-chronic
Some shorten your life by half an hour, every single day. David Spiegelhalter called these microlives (ml) — each one worth 30 minutes of life expectancy.
Smoking 20 cigarettes a day costs 10 microlives. That is 10 × 30 = 300 minutes = 5 hours of life, lost every 24 hours. A heavy smoker lives as though the day were only 19 hours long.
The scale works in reverse too. 150 minutes of weekly exercise gains 3 ml/day. Five servings of fruit and vegetables: +4 ml/day — yes, diet can outweigh exercise in Spiegelhalter’s estimates (both from the BMJ 2012 paper). A Mediterranean diet: +2 ml/day.
Hover over the bars to explore. Red = life lost. Green = life gained.
How do you compare a skydive to a cigarette? One kills instantly (rarely). The other kills slowly (certainly, at scale).@cr-bridge
The answer is Loss of Life Expectancy (LLE) — the average time lost or gained per exposure.
One micromort costs roughly 21 minutes of life expectancy. One microlife is 30 minutes. So 1 mm ≈ 0.7 ml.
The UK Department for Transport values a micromort at £1.60. NICE values a microlife at £1.70. Two independent government agencies, nearly the same price for a unit of risk.
| Unit | Abbreviation | Definition | Example |
|---|---|---|---|
| Micromort | mm | 1-in-a-million death probability | Skydiving (per jump) = 10 mm |
| Microlife | ml/day | 30 min of life expectancy per day | Smoking 2 cigs/day = −1 ml/day |
| LLE | min | Loss of Life Expectancy | 1 mm ≈ 21 min ≈ 0.7 ml |
| £ value | £ | NICE/DfT policy valuation | 1 mm ≈ £1.60 ≈ 1 ml/day |
You now have three currencies for risk — micromorts (mm), microlives (ml/day), and loss of life expectancy (LLE).@cr-quiz
You know that coffee is 0.01 mm and Everest is ~38,000 mm. You know that smoking costs 10 ml/day and exercise gains 3 ml/day. But how good is your intuition? Three quizzes, three formats:
☠️ Micromort Quiz — which activity is riskier? Pick A or B. Covers acute risks from skydiving to surgery.
⏳ Microlife Quiz — which daily habit has the bigger effect on your lifespan? Smoking vs diet vs exercise.
📊 Rank Risks Quiz — drag and drop 4 items into the correct order. Mixes acute and chronic risks on the same scale.
Which event is more likely to kill you?
Which daily habit has the bigger effect?
Rank 4 risks from biggest to smallest effect.
R version 4.6.1 (2026-06-24)
Platform: x86_64-pc-linux-gnu
Running under: Ubuntu 26.04 LTS
Matrix products: default
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time zone: Etc/UTC
tzcode source: system (glibc)
attached base packages:
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other attached packages:
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