The short answer
Official US planning guidance splits the area around a nuclear explosion into a severe, moderate and light damage zone. For a 10 kiloton explosion at ground level, FEMA puts them at about half a mile, half a mile to a mile, and one to three miles. Beyond that, windows can break for miles and fallout can travel tens of miles downwind. In every zone the first action is the same: get inside, stay inside, tune in. The UK publishes no distance figures; these are US government planning numbers.
Do this now
- Don't look towards the flash. FEMA says it can cause flash blindness over 10 miles away in daylight.
- Outside? Take cover behind anything that might protect you, or lie face down to protect your skin from heat and flying debris (Ready.gov).
- Get inside the nearest solid building once the blast wave has passed: a basement or the middle of the building, away from windows. Ready.gov says you should have 10 minutes or more before fallout arrives.
- Close doors and windows, turn off fans and air conditioning (UKHSA).
- Take off your outer clothes and bag them: UKHSA says this removes around 90% of contamination. Wash with soap or shampoo, no conditioner.
- Stay in and tune in: radio, phone alerts, GOV.UK. Be Ready says you may need to stay in for one to two days. Leave only for a fire, a collapse, a medical emergency, or if officials tell you to.
- Iodine: UKHSA says take only tablets provided for this purpose, when officials tell you to.
Prints the checklists without the menus or the map.
What this is, and what it isn't
Illustrative, based on published US planning figures, not a prediction.
- It is not a forecast of any attack, and it says nothing about how likely one is.
- There is no public list of targets: the UK Government holds its nuclear attack scenario at a higher classification (National Risk Register 2026, page 221). We don't name places or rank areas.
- The UK publishes no blast-distance figures for the public. These rings use FEMA's planning guidance (2022), scaled for other sizes with the cube-root rule from Glasstone and Dolan (1977).
- FEMA says real zones are set by what responders see on the day, and their edges won't be as sharp as any drawing.
See the zones
1 kiloton (kt) = the energy of 1,000 tonnes of TNT. FEMA's main planning case is 10 kt at ground level. Ground-level explosions only.
Click anywhere on the map to draw the rings there; click again to move them. There's no search box and no "find me" button. The point you click stays in this page: it isn't saved, sent to us or put in the web address. Map pictures come from OpenStreetMap's servers, which see which map squares your browser asks for.
| Zone | Outer edge | Where the figure comes from |
|---|---|---|
| Severe damage | about 0.5 mile (0.8 km) | FEMA, 10 kt |
| Moderate damage | about 1 mile (1.6 km) | FEMA, 10 kt |
| Light damage | about 3 miles (4.8 km) | FEMA, 10 kt |
These are planning estimates from US government guidance (FEMA 2022), scaled with the cube-root rule from Glasstone and Dolan (1977). Real damage depends on buildings, ground and weather. FEMA says zones are set by what responders see on the day.
Fallout is not drawn: it depends on the wind and can reach tens of miles downwind. Heat and burn distances are not drawn: we couldn't confirm a published table, and FEMA gives none we can use.
What to do in each zone
Severe damage zone
What it's like: FEMA: few buildings left standing; very few people above ground expected to survive; rubble blocks streets; dangerous radiation outdoors.
What to do: If you're in a strong underground space (a basement, an underground car park, a tunnel), FEMA says stay sheltered there for the first 24 hours if it's safe to do so.
Read next
Moderate damage zone
What it's like: FEMA: heavy building damage, winds over 100 mph for a moment, overturned cars, fires, some buildings collapse; sturdy concrete buildings stay up. Many injuries from flying glass and debris.
What to do: Get to the strongest part of the building, away from windows. Leave only for a fire, a collapse or a medical emergency, or when officials say. FEMA makes this zone a priority for evacuation once it is safe.
Read next
Light damage zone
What it's like: FEMA: most windows break, many hard enough to injure; fires are a major concern; power is likely to be out. Fallout will likely take 10 minutes or more to arrive.
What to do: Move away from windows. Get into a basement or the middle of a large brick or concrete building within about 10 minutes. Stay in: FEMA says 12 to 24 hours, the UK's Be Ready says you may need to stay in for one to two days.
Read next
Beyond, and downwind
What it's like: FEMA: windows facing the blast may break for many miles; flash blindness can happen over 10 miles away in daylight; dangerous fallout can reach tens of miles downwind.
What to do: Go in, stay in, tune in. Close doors and windows, turn off fans. If you were outside, take off outer clothes and bag them, then wash (no hair conditioner). Food and drink already indoors are safe (UKHSA). Iodine only if officials provide it and tell you to take it.
Read next
Live near a nuclear power station or base? That's a different hazard with its own plans: see nuclear sites, REPPIR zones and iodine. Wondering if your area is safer? Why there's no public list. How this compares with NUKEMAP: NUKEMAP explained. Iodine: should you buy tablets?
Printable checklist
Print this and keep it with your radio.
If it happens
- Don't look towards the flash. FEMA says it can cause flash blindness over 10 miles away in daylight.
- Outside? Take cover behind anything that might protect you, or lie face down to protect your skin from heat and flying debris (Ready.gov).
- Get inside the nearest solid building once the blast wave has passed: a basement or the middle of the building, away from windows. Ready.gov says you should have 10 minutes or more before fallout arrives.
- Close doors and windows, turn off fans and air conditioning (UKHSA).
- Take off your outer clothes and bag them: UKHSA says this removes around 90% of contamination. Wash with soap or shampoo, no conditioner.
- Stay in and tune in: radio, phone alerts, GOV.UK. Be Ready says you may need to stay in for one to two days. Leave only for a fire, a collapse, a medical emergency, or if officials tell you to.
- Iodine: UKHSA says take only tablets provided for this purpose, when officials tell you to.
Set up today
- Know your best room: lowest floor, middle of the building, fewest windows
- 3 days of water (3 litres per person per day) and food that needs no cooking
- A battery or wind-up FM radio, with spare batteries
- A charged power bank
- A family plan: where you'd each shelter, and one text to send
Frequently asked questions
How far does a nuclear blast reach?
FEMA's planning guide, for a 10 kiloton explosion at ground level: severe damage to about 0.5 mile, moderate damage to about 1 mile, and light damage to about 3 miles. Windows can break further out. Bigger explosions reach further, but not in proportion: FEMA says ten times the yield is typically about twice the distance.
Is this like NUKEMAP?
Similar idea, fewer rings. We draw only the three damage zones from US government planning guidance, and we don't draw fallout or burns. Our NUKEMAP explainer covers what its circles mean and where they come from.
Can I put in my town?
You can click any spot on the map to see the scale of the rings. There is no search box, and we don't name places, rank areas or say what might be a target: the UK Government holds its nuclear attack scenario at a higher classification (National Risk Register 2026), so there is no public official list. The point you click stays in your browser: it isn't saved, sent to us or put in the web address.
How long would I need to stay inside?
FEMA's planning guide says 12 to 24 hours; Ready.gov says the first 24 hours; the UK's Be Ready and UKHSA say you may need to stay indoors for one to two days. Follow official instructions on the day.
Why doesn't the UK publish these figures?
We found no UK public guidance with blast distances. UKHSA and Be Ready give the actions (go in, stay in, tune in) rather than zones, so the rings here use US government planning figures.
Should I buy iodine tablets?
UKHSA says take only the tablets provided for this purpose, and follow official advice on when to take them. Iodine only protects the thyroid against radioactive iodine, not against other radiation. Our iodine post explains more.
Why are there no fallout or burn circles?
Fallout depends on the wind on the day and can reach tens of miles downwind, so any drawing would be a guess about direction. For burns, we couldn't confirm a published distance table, and FEMA gives no figures we can use. We won't draw what we can't source.
Sources
We opened each source on the date shown. Official advice changes: if a source says something different now, follow the source. How we check facts.
- FEMA: Planning Guidance for Response to a Nuclear Detonation, Third Edition (2022; record of change 12 June 2023), PDF pages 27 to 33, 43, 44 and 64. Read from the Internet Archive copy, because fema.gov refused automated downloads (read 2 November 2026)
- Glasstone, S. and Dolan, P. J.: The Effects of Nuclear Weapons, 3rd edition (US DoD and ERDA, 1977), extract, chapter 3 note on scaling (distance scales as the cube root of the yield) (read 2 November 2026)
- UKHSA (GOV.UK): What to do in a radiation emergency (updated 10 September 2024) (read 2 November 2026)
- GOV.UK Be Ready: Hazardous substance and radiation exposure (read 2 November 2026)
- Ready.gov (FEMA): Radiation emergencies / nuclear explosion (last updated 1 July 2025) (read 2 November 2026)
- Cabinet Office: National Risk Register 2026 (PDF), page 221: the nuclear attack scenario is held at a higher classification (read 2 November 2026)
- GOV.UK: Emergency Alerts (read 2 November 2026)
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