Volcano VEI Calculator
Volcano VEI, plume, and size from ejecta.
What it does
Volcanoes earn VEI numbers by volume: each step erupts ten times the last, from gentle 0 to civilization scale 8. Famous eruptions anchor the ladder.
The tool above takes ejecta cubic kilometers. It returns VEI with plume height and a size word.
The default 1.5 km3 reads VEI 5 with plumes over 25 km. The 10 case reads VEI 6 like Pinatubo, and 0.005 reads VEI 2.
Observatory hazard programs publish the tenfold bands with example events per level. Eruption databases repeat the scale with plume columns beside.
Volume rates size while people, ash, and lahars decide harm. Observatories rate real events from deposits; this page screens bands.
How to use
- Type ejecta km3.
- Read VEI first.
- Read plume beside it.
- Read the size word last.
- Compare famous events.
- Defer to observatories.
Formula
- ejecta
- Tephra volume in cubic km.
- VEI
- 0 to 8 explosivity index.
Volcano observatory hazard programs publish the VEI scale with tenfold volume bands per index. Smithsonian eruption databases mirror the same bands with example events per level. Plume heights follow the standard column table beside volume.
Worked example
Example: 1.5 cubic km
Default: 1.5 km3 ejecta.
- Eruption: 1.5 km3 ejecta.
- Bands: each VEI spans tenfold volume.
- Band: 1 to 10 km3 reads VEI 5.
- Plume: over 25 km column.
- Word: very large eruption.
- Tool shows VEI 5, Plume over 25 km, Very large.
Reference table
| VEI | Volume | Example |
|---|---|---|
| 2 | 0.001 to 0.01 | Small |
| 5 | 1 to 10 | St. Helens |
| 6 | 10 to 100 | Pinatubo |
| 7 | 100 to 1000 | Tambora |
Limits
- Volume bands only.
- Ejecta estimates vary.
- Damage needs exposure data.
- Observatories rule ratings.
Common mistakes
- Reading VEI as damage.
- Mixing plume with volume.
- Trusting early estimates.
- Skipping lahar risks.
- Comparing across eras blindly.
Try it yourself
Quick checks. Answers sit tucked under each question.
10 km3?
VEI 6 with plumes over 25 km, colossal.
0.005 km3?
VEI 2 with 1 to 5 km plumes, explosive.
150 km3?
150 km3 reads VEI 7, super-colossal.
Questions
Volume bands?
Under 0.0001 VEI 0 through over 1000 VEI 8, tenfold each step.
Famous examples?
St. Helens 1980 VEI 5, Pinatubo 1991 VEI 6, Tambora 1815 VEI 7.
Bigger always worse?
No, VEI rates size while damage follows people, ash, and lahars.
Volume only?
Yes, plume height, qualitative notes, and tephra all feed real ratings.
Official rating?
No, this screens bands. Observatories rate events with full deposits.
VEI 8 real?
Yes, toward Yellowstone scales. No VEI 8 walks in historic time.