--- title: What Is EIRP? Formula, Examples and Australian 5GHz Limits description: EIRP explained with the formula, a worked Cisco access point example and the 5GHz EIRP limits allowed in Australia under the LIPD Class Licence. image: https://blog.iptel.com.au/hubfs/Blogs/EIRP%20vs%20Transmit%20Power/EIRP%20vs%20Transmit%20Power%20(Instagram)-feature.jpg --- [![IPTellogo-byline-2020-dark-v2-pnd-optimised-500 (1)](https://blog.iptel.com.au/hs-fs/hubfs/IPTellogo-byline-2020-dark-v2-pnd-optimised-500%20(1).png?width=200&height=59&name=IPTellogo-byline-2020-dark-v2-pnd-optimised-500%20(1).png "IPTellogo-byline-2020-dark-v2-pnd-optimised-500 (1)")](https://iptel.com.au) - [Home](https://iptel.com.au/) - [Solutions](https://iptel.com.au/solutions) Technologies - [Cisco Access Manager](https://iptel.com.au/technologies/cisco-access-manager) - [Cisco Catalyst Center](https://iptel.com.au/technologies/cisco-catalyst-center) - [Cisco Meraki](https://iptel.com.au/technologies/cisco-meraki) - [Cisco SDA Fabric](https://iptel.com.au/technologies/cisco-sda-fabric) - 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[Request a Quote](https://iptel.com.au/request-a-quote) - [Managed Services](https://iptel.com.au/managed-services-enquiry) Case Studies - [DP World Video](https://blog.iptel.com.au/hubfs/Case%20Studies/DP%20World_Case_Study.mp4) - [DP World](https://blog.iptel.com.au/dp-world-case-study) - [Backup Assure](https://blog.iptel.com.au/backup-assure-a-disaster-recovery-case-study) [Contact Us](https://iptel.com.au/contact-us) This is a search field with an auto-suggest feature attached. - There are no suggestions because the search field is empty. ## What is EIRP: EIRP vs Transmit Power May 23, 2025 Cisco shows you a power level from 1 to 8, but what is your access point actually radiating? In this blog, we'll explain EIRP vs transmit power, how to calculate EIRP, the limits that apply to 5GHz Wi-Fi in Australia, and how MIMO changes the maths. ![EIRP vs transmit power on a Cisco access point](https://blog.iptel.com.au/hs-fs/hubfs/Blogs/EIRP%20vs%20Transmit%20Power/EIRP%20vs%20Transmit%20Power-still.jpg?width=1440&height=810&name=EIRP%20vs%20Transmit%20Power-still.jpg) --- ## EIRP: What Is It and Why Does It Matter? [![Wi-Fi Channel Power: Not All Channels Are the Same](https://blog.iptel.com.au/hs-fs/hubfs/Blogs/Wi-Fi%20Channel%20Power/Not%20All%20Channels%20are%20the%20Same%20(Instagram).png?width=173&height=173&name=Not%20All%20Channels%20are%20the%20Same%20(Instagram).png)](https://blog.iptel.com.au/wi-fi-channel-power)[EIRP (Equivalent Isotropically Radiated Power)](https://en.wikipedia.org/wiki/Effective_radiated_power) is the power that actually leaves the antenna, after cable loss and antenna gain are taken into account. Transmit power is only what the radio produces. Regulators set limits on what is radiated, so EIRP is the number that keeps you legal. Cisco describes the power an AP runs at as a power level. That's handy for day-to-day tuning, but it doesn't tell you the EIRP. The regulatory domain and the gain of the antenna both play a part. The figures in this blog are for Australia. If you're reading from overseas, your regulatory domain will likely be different. Related reading - [Wi-Fi Terminology](https://blog.iptel.com.au/wi-fi-terminology) - [Wi-Fi Channel Power: Not All Channels Are the Same](https://blog.iptel.com.au/wi-fi-channel-power) --- ## Cisco Power Levels: What Is Your AP Transmitting At? Cisco APs report a power level, normally 1 to 8 (1 to 6 on some APs), where level 1 is the highest power. Each level maps to a transmit power in dBm, and the available levels depend on the AP model, the band and the channel. You can see the mapping from the controller command line. On a Cisco Wireless LAN Controller (WLC), the AireOS command "show advanced 802.11a txpower" (or "802.11b" for 2.4GHz) lists every AP radio in that band, with its current channel and transmit power. On a Catalyst 9800 controller, "show ap dot11 5ghz summary" gives the same view. The numbers in square brackets are the available transmit power options in dBm. They correspond to Cisco power levels 1 to 8, or 1 to 5 if the power is restricted on that channel. In other words, the same AP can have a different maximum on different channels. That's worth knowing before you compare two APs and wonder why one looks weaker. Related reading - [Wi-Fi Channel Power: Not All Channels Are the Same](https://blog.iptel.com.au/wi-fi-channel-power) - [RF Tuning: Access Point Power Caps](https://blog.iptel.com.au/access-point-power-caps) --- ## EIRP Formula: How Do You Calculate It? [![RF Tuning: Access Point Power Caps](https://blog.iptel.com.au/hs-fs/hubfs/Blogs/AP%20Power%20Caps/Access%20Point%20Power%20Caps%20(Instagram).gif?width=173&height=173&name=Access%20Point%20Power%20Caps%20(Instagram).gif)](https://blog.iptel.com.au/access-point-power-caps)EIRP is the transmit power of the AP radio, minus any cable loss between the transmitter and the antenna, plus the antenna gain. Transmit power and EIRP are in dBm, cable loss in dB and antenna gain in dBi, so you simply add and subtract. **EIRP = TxPower (dBm) − Cable Loss (dB) + Antenna Gain (dBi)** For example, take a 20dBm (100mW) transmitter with a 2dBi internal antenna, where cable loss is negligible. The EIRP is 22dBm. Who sets the limits? The local regulator: the FCC in the United States, ETSI in Europe, and the ACMA (Australian Communications and Media Authority) here. Regulators define a maximum transmit power, a maximum EIRP, or both. In Australia, the ACMA defines only the maximum EIRP. Related reading - [Cisco 9124 Antenna Guide](https://blog.iptel.com.au/cisco-9124-antenna-guide) - [Comparing Cisco AP Coverage Patterns](https://blog.iptel.com.au/comparing-cisco-ap-coverage-patterns) --- ## EIRP Limits: What Australia Allows on 5GHz In Australia, Wi-Fi operates under the ACMA's Low Interference Potential Devices (LIPD) class licence, which sets a maximum EIRP for each part of the 5GHz band. The limits range from 200mW (23dBm) in the lower channels up to 4W (36dBm) in the upper band, as the table below shows. The values below come from Schedule 1, Table 8 of the [LIPD Class Licence 2025](https://www.legislation.gov.au/F2025L01047/asmade). The 5150–5350MHz channels are indoor-only, the 5250–5350 and 5470–5725MHz channels must use DFS, and 5600–5650MHz is left out to protect weather radar. | **Band** | **Frequency (MHz)** | **mW** | **dBm** | | --- | --- | --- | --- | | UNII-1 | 5150–5250 | 200 | 23 | | UNII-2A | 5250–5350 | 200 | 23 | | UNII-2C | 5470–5600 | 1000 | 30 | | UNII-2C | 5650–5725 | 1000 | 30 | | UNII-3 / ISM | 5725–5850 | 4000 | 36 | **Table 1: Maximum EIRP for 5GHz Wi-Fi in Australia** Remember, these are EIRP values. The Cisco transmit power values we looked at earlier are not EIRP, so you have to add the antenna gain (and subtract cable loss if you're using external antennas on coax). For legacy, pre-802.11n access points with a single radio chain, the formula above is all you need. The diagram below shows how transmit power and EIRP relate. ![Diagram comparing Wi-Fi transmit power with EIRP after antenna gain and cable loss](https://blog.iptel.com.au/hs-fs/hubfs/Blogs/EIRP%20vs%20Transmit%20Power/Wi-Fi%20EIRP%20vs%20Transmit%20Power.gif?width=1440&height=810&name=Wi-Fi%20EIRP%20vs%20Transmit%20Power.gif) Related reading - [Reduce Wi-Fi Congestion With DFS](https://blog.iptel.com.au/reduce-wifi-congestion-with-dfs) - [Wi-Fi and the Problem With RADAR (DFS)](https://blog.iptel.com.au/wifi-and-the-problem-with-radar) --- ## MIMO: How Multiple Radio Chains Change the Maths [![How Does Cisco AI-Enhanced RRM Work](https://blog.iptel.com.au/hs-fs/hubfs/Blogs/How%20does%20Cisco%20AI-RRM%20Work/How%20does%20Cisco%20Ai-RRM%20Work%20(Instagram).gif?width=173&height=173&name=How%20does%20Cisco%20Ai-RRM%20Work%20(Instagram).gif)](https://blog.iptel.com.au/how-does-ai-enhanced-rrm-work)From 802.11n onwards, APs use MIMO (Multiple Input, Multiple Output), with several radio chains transmitting at once. Their combined output adds a multi-chain gain, so in most regulatory domains the allowed power is shared across the chains. A 4x4 MIMO AP has to be calculated differently from a single-chain AP. The formula becomes: **EIRP = TxPower (dBm) + Multi-Chain Gain (dB) − Cable Loss (dB) + Antenna Gain (dBi)** The multi-chain gain depends on the number of transmit chains and how the regulator treats them. It can be up to 10 × log10(N) dB for N chains, which is about 6dB for four chains. In the worked examples below, 4dB is allowed for the four transmit chains. Take the Cisco 3702i, a 4x4 MIMO AP (an older model, but the maths still applies), configured for the Australian regulatory domain. Its UNII-1 maximum transmit power of 15dBm equates to 23dBm EIRP, exactly the ACMA maximum. **23dBm = 15 (dBm) + 4 (dB) − 0 (dB) + 4 (dBi)** Its UNII-3 maximum transmit power of 23dBm equates to 31dBm EIRP. That's short of the 36dBm ACMA maximum, because 23dBm is the most the 3702i can physically transmit. **31dBm = 23 (dBm) + 4 (dB) − 0 (dB) + 4 (dBi)** **Pro-Tip:** If your numbers still aren't adding up, check the PoE. Some Cisco 4x4 MIMO access points fall back to 3x3 when they only get standard PoE (Power over Ethernet, 802.3af) rather than PoE+ (802.3at). Related reading - [How Does Cisco AI-Enhanced RRM Work](https://blog.iptel.com.au/how-does-ai-enhanced-rrm-work) - [Wi-Fi Design and the Cinema Story](https://blog.iptel.com.au/wifi-and-the-cinema-story) --- ## EIRP vs Transmit Power: FAQs ### What Is EIRP? EIRP (Equivalent Isotropically Radiated Power) is the power radiated from an antenna, calculated as transmit power minus cable loss plus antenna gain, plus multi-chain gain for MIMO APs. Regulators such as the ACMA set their Wi-Fi limits as EIRP. ### What Is the Difference Between EIRP and Transmit Power? Transmit power is what the AP radio produces. EIRP is what actually radiates from the antenna once cable loss, antenna gain and multi-chain gain are included. The Cisco power level you see on an AP maps to transmit power, not EIRP. ### Does Antenna Gain Count Towards EIRP? Yes. Antenna gain is added straight onto the transmit power, so a higher-gain antenna means a higher EIRP for the same radio setting. That's why external antennas need care: it's possible to exceed the legal limit without touching the AP's power level. ### Why Don't My APs Run at Maximum Power? Cisco Radio Resource Management (RRM) includes Transmit Power Control (TPC), which turns AP power down so neighbouring APs don't overlap too much. On a well-designed network, few APs should be running at their maximum. --- ## EIRP vs Transmit Power: Summary The power an AP is allowed to radiate is set by the regulatory domain, which fixes the maximum EIRP per channel, and EIRP includes antenna gain, cable loss and multi-chain gain as well as the radio's transmit power. Get the calculation right and you stay legal while getting the coverage you designed for. Cisco's Transmit Power Control means most APs won't sit at maximum anyway, which is another reason to treat the power level as a starting point, not the full story. ### Need Help With Wi-Fi Power and EIRP? Our [Wi-Fi survey and design team](https://iptel.com.au/services/wi-fi-surveys) can check your AP power settings, antennas and channel plan against your site and the Australian limits. If that would be useful, [get in touch with the IPTel team](https://iptel.com.au/contact-us) or email [sales@iptel.com.au](mailto:sales@iptel.com.au). #### Related Articles ###### [Reduce Wi-Fi Congestion with DFS](https://blog.iptel.com.au/reduce-wifi-congestion-with-dfs) June 19, 2025 ###### [Wi-Fi and The Problem With RADAR (DFS)](https://blog.iptel.com.au/wifi-and-the-problem-with-radar) July 21, 2025 ###### [Comparing Cisco AP Coverage Patterns](https://blog.iptel.com.au/comparing-cisco-ap-coverage-patterns) May 11, 2026 Free tool ### How Many Wi-Fi Access Points Do You Need? Work out APs, PoE and switch ports floor by floor, using the same survey grades our Cisco wireless engineers design to. Takes under a minute. [Try the AP Estimator →](https://iptel.com.au/resources/wifi-access-point-estimator?utm_source=blog&utm_medium=cta&utm_campaign=ap-estimator) ```json { "@context" : "https://schema.org", "@type" : "BlogPosting", "author" : { "@type" : "Person", "name" : "Mark McSherry", "url" : "https://blog.iptel.com.au/author/mark-mcsherry" }, "dateModified" : "2026-10-11T05:23:08.320Z", "datePublished" : "2025-05-23T05:22:05.000Z", "headline" : "What Is EIRP? Formula, Examples and Australian 5GHz Limits", "image" : [ "https://blog.iptel.com.au/hubfs/Blogs/EIRP%20vs%20Transmit%20Power/EIRP%20vs%20Transmit%20Power%20(Instagram)-feature.jpg" ], "mainEntityOfPage" : { "@id" : "https://blog.iptel.com.au/what-is-eirp-eirp-vs-transmit-power", "@type" : "WebPage" }, "publisher" : { "@type" : "Organization", "logo" : { "@type" : "ImageObject", "url" : "https://blog.iptel.com.au/hubfs/IPTel_Solutions_February2020%20-%20Header%20SiteMap/Images/IPTellogo-byline-2020-dark-v2.png" }, "name" : "IPTel Solutions Pty Ltd" } } ```