5G Speeds in Practice vs What Is Advertised: The Reality

Where the Advertised Numbers Come From

Mobile operators publish peak 5G speeds based on the theoretical maximum throughput that the air interface can support under optimal conditions. These figures are derived from the 3GPP technical specifications that define how 5G New Radio (NR) operates, and they assume a single device using all available channel bandwidth with no interference, full signal power, and the highest modulation scheme. In the UK, peak claims have ranged from around 300 Mbps at the lower end to figures exceeding 1 Gbps for networks deploying wider spectrum allocations or carrier aggregation across multiple frequency bands.

Advertising rules require that headline speed claims be achievable by a defined proportion of users at peak time, but for mobile services the Advertising Standards Authority applies more flexible rules than those governing fixed broadband (where the “average” must reflect the speed at least 50 percent of customers receive at peak hours). For 5G, operators are permitted to cite theoretical or peak figures when they are clearly labelled as such, which means the number on the poster may reflect performance that very few users will encounter in ordinary use.

What Ofcom Data Actually Shows

Ofcom publishes its Connected Nations reports annually, alongside interim updates, which include measured 5G download and upload speeds drawn from handset-based testing across UK networks. The methodology involves crowd-sourced and panel-based measurement, capturing performance in real conditions across different times of day, locations, and device types. These figures provide the most authoritative picture of what consumers actually experience rather than what is theoretically possible.

Across the major UK operators, Ofcom data has recorded median 5G download speeds broadly in the range of 50 Mbps to 200 Mbps, depending on the network, location, and the spectrum band in use. Upload speeds are typically lower, often in the 20–50 Mbps range. Crucially, these medians mask wide variation: a user in a dense urban area with line-of-sight to a 5G mast and no congestion may see several hundred megabits per second, while a user indoors at the edge of coverage may see speeds closer to 4G levels—or lower if the device is struggling to maintain a 5G connection at all.

Why the Gap Between Theory and Reality Is So Large

Several compounding factors account for the difference between peak theoretical speeds and typical delivered speeds. First, spectrum is shared: a 5G cell sector serves all devices simultaneously, so the aggregate capacity is divided among active users. In a busy area at peak time, each device receives a smaller slice of available bandwidth. Second, signal quality degrades with distance from the mast, with physical obstructions, and through building materials. Lower signal quality forces the device to use a more robust (but slower) modulation and coding scheme, directly reducing throughput.

Third, most UK 5G deployments use sub-6 GHz spectrum—primarily the 3.4–3.8 GHz “C-band” and, to a lesser extent, 700 MHz for coverage. These bands offer good propagation but do not deliver the multi-gigabit speeds associated with millimetre-wave (mmWave) at 26 GHz and above. Finally, the core network, backhaul links connecting masts to the wider internet, and server-side constraints all impose ceilings that are unrelated to the air interface. A 5G connection to a congested server will perform no better than 4G to the same server.

Sub-6 GHz vs mmWave: Two Very Different Technologies

The term “5G” covers a range of frequency bands with fundamentally different characteristics. Sub-6 GHz deployments—particularly the 3.4–3.8 GHz C-band that forms the backbone of UK 5G networks—use frequencies that propagate over hundreds of metres and can pass through glass and some building materials, albeit with losses. This makes sub-6 GHz practical for city-wide and suburban coverage using existing mast infrastructure. Typical channel widths of 50–100 MHz in this band can realistically deliver peak cell speeds in the hundreds of megabits per second range, shared across connected users.

Millimetre-wave 5G, operating around 26 GHz in the UK (Ofcom awarded spectrum in this band in 2019), behaves quite differently. The very short wavelengths allow extremely wide channel bandwidths—up to 400 MHz per carrier—enabling multi-gigabit peak speeds. However, 26 GHz signals attenuate rapidly with distance and are almost entirely blocked by walls, glass, and even foliage. Practical mmWave deployments are limited to outdoor hotspots at very short range, typically tens of metres. As of 2026, UK mmWave deployment remains extremely limited compared with sub-6 GHz, meaning very few consumers will encounter it in ordinary use.

Indoor vs Outdoor: A Consistent Performance Divide

One of the most consistent findings in Ofcom’s measurement work is that 5G performance indoors is materially lower than outdoors on the same network. The 3.5 GHz band used by most UK 5G operators suffers greater building penetration loss than the 800 MHz or 1800 MHz bands that underpin 4G indoor coverage. Concrete, brick, and metal in modern buildings can attenuate 3.5 GHz signals by 20–30 dB, which may be enough to push an indoor device off 5G entirely and onto 4G or even 3G fallback.

Operators are addressing indoor coverage through a combination of approaches: deploying 5G on 700 MHz (which propagates better into buildings), installing small cells within large venues such as stations and arenas, and expanding coverage using the Shared Rural Network (SRN) programme. However, for the majority of residential users, indoor 5G performance is likely to remain lower than outdoor performance for some years, and relying on a home Wi-Fi connection will often outperform a 5G cellular connection indoors.

When 5G Speed Actually Makes a Practical Difference

For many everyday mobile tasks, the speed difference between good 4G and real-world 5G is invisible. Browsing a webpage, sending a message, or making a video call requires tens of megabits at most—well within 4G capability in a good coverage area. The practical benefits of 5G speed become apparent in a narrower set of scenarios: downloading a large application or software update in seconds rather than minutes; streaming very high-resolution video or cloud gaming with minimal buffering on a mobile data connection; and using a 5G MiFi device as a temporary home broadband substitute where fixed-line speeds are poor.

Latency is a dimension where 5G offers measurable improvement even at moderate speeds. The theoretical latency of 5G NR is lower than 4G LTE at the air interface, and while real-world improvements are modest compared with the theoretical figures, users engaged in real-time gaming, voice calls over cellular, or latency-sensitive applications may notice a qualitative improvement. Ofcom’s data suggests 5G median latency is meaningfully lower than 4G on the same network, even when the throughput advantage is not dramatic.

What This Means in Practice

Consider Priya, who commutes daily between Coventry and Birmingham. She has a 5G-capable handset on a plan that includes 5G access. On the train platform in central Birmingham, her phone shows a 5G connection and she routinely downloads a podcast episode of around 200 MB in under 20 seconds—a throughput consistent with Ofcom’s typical urban outdoor 5G range. Once she boards the train and moves through suburban areas and tunnels, the connection drops to 4G and her download speeds fall to the 15–25 Mbps range. At her office in a 1970s concrete building, her phone shows 4G despite the area having outdoor 5G coverage, because the 3.5 GHz signal cannot adequately penetrate the structure. Her experience is entirely consistent with the gap between advertised peak and real-world delivered performance—5G is fast and useful in outdoor urban settings, but 4G-comparable or worse in buildings and areas of incomplete coverage.

How We Verified This

This article draws on Ofcom’s Connected Nations reports and updates, which include measured 5G speed data from handset-based testing across UK networks; Ofcom’s spectrum award documentation for the 3.4–3.8 GHz and 26 GHz bands; the 3GPP 5G NR technical specifications (Release 15 and later) as the basis for theoretical peak claims; and the Advertising Standards Authority’s guidance on broadband and mobile speed advertising. WHO and ICNIRP documentation was reviewed for context on spectrum band definitions.

Frequently Asked Questions

How fast is 5G in practice?

Based on Ofcom’s connected nations measurement data, typical UK 5G users in populated areas receive median download speeds broadly in the range of 50–200 Mbps, depending on the operator, location, and whether they are indoors or outdoors. This is materially faster than 4G in comparable conditions, but significantly below the 1 Gbps or higher figures operators cite as peak theoretical performance.

Why is my 5G not as fast as advertised?

Advertised peak 5G speeds assume ideal lab conditions: a single device, full signal strength, no congestion, and the widest possible channel bandwidth. In real use, spectrum is shared between all connected devices, signal degrades with distance and through walls, and the wider internet infrastructure imposes its own limits. These factors together mean that typical delivered speeds are a fraction of the advertised maximum, which is consistent with Ofcom’s published measurement data.

What is the difference between 5G sub-6 GHz and mmWave?

Sub-6 GHz 5G (primarily the 3.4–3.8 GHz C-band in the UK) uses frequencies that propagate over hundreds of metres and offer reasonable building penetration, making it suitable for wide area coverage. Millimetre-wave 5G (around 26 GHz in the UK) can deliver multi-gigabit speeds but has a very short range, is blocked by most solid surfaces, and remains extremely limited in deployment across UK public networks as of 2026.

When do I actually notice 5G speed?

The benefit is most tangible when downloading large files (apps, video, software updates), streaming high-resolution video on mobile data, or using a 5G router as a broadband substitute. For routine browsing, messaging, and standard-definition streaming, the speed difference over 4G is typically imperceptible because both technologies easily exceed the bandwidth the task requires. Lower latency on 5G may also be noticeable in real-time gaming or voice applications.

Is 5G faster than home fibre broadband?

In outdoor urban conditions with good 5G signal, typical speeds can match or briefly exceed those of mid-tier home fibre packages. However, home full-fibre (FTTP) services consistently offer higher and more stable throughput, lower latency, and are unaffected by mobile network congestion. For sustained high-demand use, fixed fibre remains the more reliable option; 5G excels as a mobile or backup connection rather than a direct fibre substitute for most households.

Sources

• Ofcom – Connected Nations reports
• Ofcom – 700 MHz and 3.6 GHz spectrum award
• Ofcom – 26 GHz spectrum award
• Advertising Standards Authority – Broadband and mobile speed guidance
• 3GPP – 5G New Radio technical specifications