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Solar Flare X-Ray Class Converter

Convert a solar flare class such as M5.2 or X1.0 to X-ray flux in W/m² and back, with the NOAA radio blackout scale.

Flare class (for example M5.2)

X-ray flux, 0.1-0.8 nm (W/m²)

Flare classes and radio blackouts

Class	Peak flux (W/m²)	NOAA scale	HF effect on the sunlit side
A	below 10^-7	-	None
B	10^-7 to 10^-6	-	None
C	10^-6 to 10^-5	-	Negligible
M1 to M4	10^-5 to 5×10^-5	R1 Minor	Weak, brief degradation
M5 to M9	5×10^-5 to 10^-4	R2 Moderate	Limited blackout, tens of minutes
X1 to X9	10^-4 to 10^-3	R3 Strong	Wide-area blackout, about an hour
X10 to X19	10^-3 to 2×10^-3	R4 Severe	Blackout for one to two hours
X20 and above	2×10^-3 and above	R5 Extreme	Complete blackout for hours

Each letter is ten times stronger than the one before; the number is a multiplier within the class. See the guide to solar flares and radio blackouts and the current flux on the live data page.

Data: NOAA Space Weather Prediction Center, NASA SDO. Band conditions are estimates computed by Map For HAM and are indicative only. Methodology and credits · Data feeds · Widgets