External Dose Calculator


Click "Begin Session" to start calculating your ingestion-based gamma dose. To calculate your dose, you will need to

  1. Select the location you have visited or plan to visit.
  2. On the map, click the top left corner of the specific area you visited or plan to visit.
  3. On the map, click the bottom right corner of the specific area you visited or plan to visit.
  4. Click Draw. 
    • If the area highlighted on the map is not accurate, click Clear and repeat steps 1-4.
  5. Once the highlighted area accurately reflects your visit, click Submit.
  6. Enter the date(s) you spent or plan to spend in the area.
  7. Enter the amount of time you spent or plan to spend in the area.
  8. Click Submit.

You can select multiple areas on multiple islands. Your calculated dose for each area will be stored until your session ends.






Data Point Key

  • : Village
  • : Other
  • : House
  • : Airport
  • : Island Interior
  • : Beach
Date at selected area
Hours in village
Hours in island interior
Hours at other location
Hours in house
Hours at airport
Hours at beach
ID Island Atoll Date Total Hours Time-Weighted Estimated
External Gamma Dose



The main contribution to the external gamma dose rates on nuclear affected islands and atolls in the Marshall Islands is residual levels of cesium-137 contamination in soil. Most in-situ monitoring techniques for determining external exposure rates from cesium-137 in soil require knowledge about the depth distribution (gamma relaxation length and half-value layer) of cesium-137 in the soil to correct for scattering of photons from decay of any buried cesium-137. The scattered Compton radiation often causes significant overdose reporting using direct output from simple mR meters and underdose reporting using 661 keV peak dose data from scintillation or high-resolution detector systems with energy/peak search functionality.

The Marshall Islands Program periodically conducts field surveys of islands and atolls using in-situ gamma spectrometers to measure external gamma dose rate contributions from cesium-137 at a height of 1 meter above the ground. The data on this website are largely derived from static dose rate measurements taken directly from Model 935 Surveillance and Measurement systems supplied by Berkeley Nucleonics with no further corrections applied. Detailed analyses of these data under more standard convention and practice with applicable corrections will be reported separately.

For comparative purposes, we also provide a nominal annual external dose estimate in units of millisievert (mSv) per year for a full year of occupancy on the main residence islands. 1 millisievert (1 mSv) is equal to 100 millirem (1 mrem).

Estimates are based on observations of people's living habits and use a normalized average distribution of people's time in various locations on the island, e.g., percentage of time spend in a house, around the village and housing area, on the beach or lagoon, and/or on the interior of the island.

In general, the external dose component normally contributes about 10 to 15 percent of the total nuclear test-related dose. The most significant fraction of the nuclear test related dose comes from internal exposure from ingestion of cesium-137 contained locally grown tree crops such as coconut, breadfruit, and Pandanus fruit.