Antennas, Antenna Cables, Wireless Products: Technical Articles
ISM Band Frequencies & Allocation: 433 MHz, 915 MHz, 2.4 GHz & 5.8 GHz Explained
ISM Band Frequencies and Allocation Explained
The ISM band frequencies are license-free radio and microwave allocations reserved by regulators for Industrial, Scientific and Medical equipment. The most widely used ISM bands are 433 MHz, 915 MHz, 2.4 GHz and 5.8 GHz, but the full set ranges from 6.78 MHz up to 245 GHz. Because most of these allocations can be used without an individual transmitting license, they have become the backbone of nearly every unlicensed wireless technology — Wi-Fi, Bluetooth, Zigbee, LoRa, RFID and cordless telemetry all operate in ISM spectrum.
What Does ISM Band Mean?
ISM stands for Industrial, Scientific and Medical. The term describes a group of radio frequency (RF) bands that the International Telecommunication Union (ITU) set aside for equipment that generates RF energy for purposes other than communications — such as industrial heating, MRI machines, RF test equipment, microwave ovens and medical diathermy. Over time, low-power communication devices were permitted to share this spectrum on a "no-protection, no-interference" basis, which is how Wi-Fi and Bluetooth came to live in the 2.4 GHz ISM band.
Devices operating in an ISM band must accept any interference received from other ISM equipment and must not cause harmful interference to licensed services. That trade-off is the price of avoiding per-device licensing, and it is why dense 2.4 GHz environments can become congested.
ISM Band Frequencies: Allocation Table
The table below lists the primary ISM band frequencies defined by the ITU Radio Regulations, their center frequency and typical uses. Regional regulators (FCC in the USA, ETSI in Europe) apply their own power limits and duty-cycle rules on top of these allocations, so always confirm the rules for your deployment country.
| Frequency Range | Center Frequency | Availability / Region | Typical Uses |
|---|---|---|---|
| 6.765–6.795 MHz | 6.78 MHz | Subject to local acceptance | Industrial RFID, inductive heating |
| 13.553–13.567 MHz | 13.56 MHz | Worldwide | HF RFID, NFC, access cards |
| 26.957–27.283 MHz | 27.12 MHz | Worldwide | CB radio, RC models, diathermy |
| 40.66–40.70 MHz | 40.68 MHz | Worldwide | Low-power telemetry, remote control |
| 433.05–434.79 MHz | 433.92 MHz | ITU Region 1 (EU, Africa) | LoRa (EU), remote keyless entry, telemetry |
| 902–928 MHz | 915 MHz | ITU Region 2 (Americas) | LoRa/LoRaWAN (US), Zigbee, 900 MHz RFID |
| 2.400–2.500 GHz | 2.45 GHz | Worldwide | Wi-Fi, Bluetooth, Zigbee, microwave ovens |
| 5.725–5.875 GHz | 5.8 GHz | Worldwide | Wi-Fi, fixed wireless, cordless telemetry |
| 24.00–24.25 GHz | 24.125 GHz | Worldwide | Motion sensors, radar, industrial |
Allocations are defined by the ITU; local power and duty-cycle limits vary by region. The 433 MHz and 915 MHz bands are notably region-specific — 915 MHz is available in the Americas while 433 MHz is the comparable low-power band in Europe.
The Most Important ISM Bands in Practice
2.4 GHz ISM Band
The 2.400–2.500 GHz band is the most widely used ISM allocation because it is available license-free worldwide. It carries Wi-Fi (802.11b/g/n/ax), Bluetooth, Zigbee and Thread, alongside microwave ovens and cordless devices. Its popularity is also its weakness: the 2.4 GHz band is crowded, which raises the noise floor and makes antenna selection and placement critical. See our 2.4 GHz antennas and dual-band 2.4/5 GHz antennas.
915 MHz and 433 MHz Sub-GHz ISM Bands
Sub-GHz ISM bands propagate farther and penetrate buildings better than 2.4 GHz, which is why long-range IoT protocols such as LoRa and LoRaWAN use 915 MHz in North America and 868/433 MHz in Europe. These bands trade data rate for range and power efficiency. Match them with purpose-tuned hardware such as LoRa / LoRaWAN antennas and 433 MHz antennas.
5.8 GHz ISM Band
The 5.725–5.875 GHz band overlaps the upper portion of the 5 GHz Wi-Fi spectrum and is used for high-throughput Wi-Fi and point-to-point fixed wireless links. Higher frequency means more available bandwidth but shorter range and lower obstruction penetration than the sub-GHz bands.
Why ISM Bands Reduce Interference With Licensed Services
Most licensed telecommunication services operate outside the ISM allocations. By confining unlicensed equipment to designated ISM bands, regulators keep high-RF-energy devices such as microwave ovens away from licensed cellular, broadcast and public-safety spectrum. In practice this is why a wireless router and a cellular phone can operate in the same room without interfering with each other — they occupy different parts of the spectrum.
Choosing Antennas and Cables for ISM Band Operation
Every ISM band has its own antenna and cable requirements. The antenna must be tuned to the band's center frequency, and the coaxial cable and connectors must preserve signal with low loss — especially at 2.4 GHz and 5.8 GHz, where cable attenuation rises sharply. For band-specific hardware, browse Data Alliance's antennas, antenna cables and adapters, and band-pass filters that reject out-of-band interference. If you need a cable built to an exact length and connector combination, request a custom quote from our technical team.
Frequently Asked Questions About ISM Band Frequencies
What does ISM stand for?
ISM stands for Industrial, Scientific and Medical. It describes radio frequency bands that the ITU reserved for equipment generating RF energy for purposes other than telecommunications, which low-power communication devices were later allowed to share without an individual license.
What are the most common ISM band frequencies?
The most widely used ISM bands are 433 MHz, 915 MHz, 2.4 GHz and 5.8 GHz. The 2.4 GHz band is the most common because it is license-free worldwide and carries Wi-Fi, Bluetooth and Zigbee.
Do I need a license to transmit in the ISM band?
In most countries you do not need an individual transmitting license to operate low-power equipment within an ISM band, provided the device complies with the local regulator's power and duty-cycle limits (for example, FCC Part 15 rules in the USA). ISM users must accept interference from other ISM equipment.
Why is the 433 MHz band used in Europe but 915 MHz in the Americas?
ISM allocations are region-specific under the ITU framework. The 902–928 MHz (915 MHz) band is allocated in ITU Region 2 (the Americas), while 433 MHz is the comparable low-power band in ITU Region 1 (Europe and Africa). This is why LoRa hardware is sold in region-specific frequency variants.
Is the 2.4 GHz Wi-Fi band the same as the ISM band?
Yes. The 2.400–2.500 GHz Wi-Fi band sits entirely within the 2.4 GHz ISM allocation, which is also why Wi-Fi, Bluetooth and microwave ovens share and sometimes interfere with one another in that spectrum.
