What are the ISM bands?
The ISM bands are frequency ranges designated in the ITU Radio Regulations for industrial, scientific and medical RF energy applications such as heating, in which radio services must accept interference. Footnote 5.150 lists bands including 13.553–13.567 MHz, 26.957–27.283 MHz, 40.66–40.70 MHz, 902–928 MHz (Region 2), 2400–2500 MHz, 5725–5875 MHz and 24–24.25 GHz; footnote 5.138 lists bands needing special authorization, such as 6.765–6.795 MHz, 433.05–434.79 MHz (Region 1), 61–61.5 GHz, 122–123 GHz and 244–246 GHz.[1]
Why do unlicensed radios use ISM bands?
National regulators permit low-power unlicensed communication devices in or near ISM bands, under rules such as FCC Part 15 (e.g., 15.247 in 902–928, 2400–2483.5 and 5725–5850 MHz). Wi-Fi, Bluetooth, Zigbee and many IoT radios operate here and must tolerate interference, including from microwave ovens at 2.45 GHz.[2]
What are the regional differences?
The 902–928 MHz band is ISM only in ITU Region 2 (Americas); Europe uses short-range device bands around 863–870 MHz instead (not ISM). 433.05–434.79 MHz is an ISM band in Region 1. Always check national rules.[1]
Is ISM the same as unlicensed?
Not exactly: ISM designation concerns non-communication RF energy use; unlicensed communications rules are separate national provisions that often, but not always, coincide with ISM bands (U-NII at 5 GHz and 6 GHz are not ISM).
Frequently asked questions
Is 2.4 GHz ISM 2400–2483.5 MHz?
The ITU ISM band is 2400–2500 MHz; FCC Part 15.247 communications use 2400–2483.5 MHz.
Is 868 MHz an ISM band?
No; it is a European short-range device band.
Why 2.45 GHz for microwave ovens?
It lies in the ISM band and heats water effectively with practical magnetrons.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “Radio Regulations”. International Telecommunication Union (ITU-R). 2024 edition.
- “47 CFR Part 15: Radio Frequency Devices”. U.S. Federal Communications Commission, via eCFR. current.