Locating Technologies
433 MHz for real-time location: how it works, range and accuracy
433 MHz (more precisely 433.05–434.79 MHz in most regions) is another unlicensed ISM/SRD (short-range device) band, lower in frequency than 900 MHz and considerably lower than 2.4 GHz. It's a long-established band for simple, low-data-rate radio devices, from remote controls and garage door openers to a range of active RFID and asset-tracking tags, particularly common in Europe, where regulatory allocation for 433 MHz has historically been more consistent than for the 900 MHz band.
Key specifications
Property | Typical value |
|---|---|
Frequency | Roughly 433.05–434.79 MHz (ISM/SRD band, region-dependent) |
Range | Often 50–100 m or more, depending on power, antenna and environment |
Accuracy | Generally room- or zone-level, typically several metres |
Measurement methods | RSSI-based proximity and zone estimation |
Update rate | Usually low, from tag battery-preserving intervals of seconds to minutes |
Tag power profile | Active tags commonly achieve multi-year battery life given low, infrequent transmission power |
As with 900 MHz, 433 MHz covers a range of largely proprietary systems rather than one unified standard, so figures vary by vendor and deployment.
How it works
433 MHz's longer wavelength, roughly 70 cm, compared with around 12.5 cm at 2.4 GHz, follows the same physical relationship described in our radio frequencies guide: lower frequency signals generally diffract more readily around obstacles and penetrate common building materials more easily than higher-frequency alternatives, for a given transmit power. This makes 433 MHz a practical choice for wide-area coverage in buildings with a lot of walls, machinery or other obstructions between tag and reader.
Most 433 MHz location systems, like their 900 MHz counterparts, rely on RSSI to estimate proximity or zone, one of the basic measurement approaches described in our measurement basics guide. A tag transmits periodically, one or more fixed readers detect it, and signal strength is used to infer roughly how close the tag is, or which reader it's nearest to. Precise ranging or angle-based measurement is uncommon at this frequency in commercial systems, partly because the narrow bandwidth typically used doesn't lend itself to the fine timing precision that technologies like UWB rely on.
Because 433 MHz has a long history as a general-purpose SRD band, interference from other unrelated devices sharing the same frequency, such as remote controls, weather stations and various consumer electronics, is a practical consideration in some environments, though the band is generally less congested than 2.4 GHz.
Measurement methods available
- RSSI-based proximity and zone estimation – the standard method used by most 433 MHz active tag systems
Advantages
- Good range and building penetration relative to transmit power, due to the longer wavelength
- Long-established, well-supported band, particularly in Europe, with a mature regulatory framework
- Long tag battery life achievable with low transmission power and infrequent updates
- Generally less congested than the 2.4 GHz ISM band
Limitations
- Accuracy is typically coarse, zone- or room-level rather than precise
- Largely proprietary systems mean limited interoperability between different vendors' tags and readers
- Narrow bandwidth limits the potential for precise timing-based ranging
- Shared use by a wide range of unrelated consumer devices can introduce occasional interference
Typical applications
433 MHz is commonly used for wide-area active asset tracking across large facilities, some active RFID deployments where long range and battery life matter more than precise position, and applications in environments with significant structural obstruction where higher-frequency signals would struggle to maintain reliable coverage.
Frequently asked questions
How does 433 MHz compare to 900 MHz for location? Both are used for similar purposes, wide-area, RSSI-based active tracking, with broadly comparable range and accuracy characteristics. The main practical difference is regional regulatory support, with 433 MHz more consistently allocated in Europe.
Is 433 MHz accurate enough for precise indoor positioning? Generally not on its own. 433 MHz systems are typically built for proximity or zone detection rather than the sub-metre precision offered by technologies like UWB or BLE AoA.
Why choose 433 MHz over 2.4 GHz? 433 MHz's longer wavelength generally gives it better range and penetration through obstructions for a given transmit power, at the cost of lower achievable accuracy and a less standardised device ecosystem.