United Kingdom · SIM-only
Compare UK SIM-only deals with 100GB or more of data, including unlimited plans, in the live offers below. A bigger allowance is only useful if the network works where you need it and the contract fits your budget. Check the ongoing price, any temporary data boost and whether the SIM suits your phone or hotspot. DealPriceCheck shows selected offers, not the whole market.
No current offers match these filters.
| Question | Short answer |
|---|---|
| What qualifies? | An offer showing at least 100GB of UK data per allowance period, or one labelled unlimited. Check whether any extra data is temporary. |
| Do I need that much? | Check three recent billing periods. Ofcom's 2026 report puts the 2025 average at 11.8GB per month per mobile-data user; your needs may be very different. |
| What is best value? | The lowest total cost for enough usable data, acceptable coverage and the contract length you want — not necessarily the lowest first payment. |
| What should I check first? | Whether the big allowance is promotional, whether it is data-only and what the tethering, speed and roaming terms actually permit. |
This page shows offers with at least 100GB of UK mobile data per allowance period, as well as offers labelled unlimited in the live catalogue. It is not a list of exactly 100GB plans. The live cards may include intermediate sizes such as 120GB, 150GB, 200GB or 300GB when those offers are available. A 100GB or 200GB bundle has a finite allowance, while unlimited is a different type of offer. These are catalogue labels, not independent verification that every unlimited plan has no fair-use, speed or device restrictions.
A wide range helps you choose, but it also makes two mistakes easy:
Use the Data, Price, Contract and Network controls above to narrow the live selection. When comparing a fixed-data offer with an unlimited one, examine the individual Full plan details rather than treating them as interchangeable.
A 100GB+ SIM can make sense if you use substantial mobile data away from Wi-Fi, frequently tether other devices or need a larger buffer for unpredictable weeks. It is likely unnecessary if your recent mobile use is consistently modest. Buying a high-data allowance you never approach can cost more without improving your signal or speed.
For perspective, Ofcom's Communications Market Report 2026 reports an average of 11.8GB a month per mobile-data user in 2025. One hundred gigabytes is roughly eight and a half times that average. But the average covers very different people; it is not a recommendation or evidence that a particular person needs less than 100GB.
If you are unsure how to estimate your own needs, our mobile data usage guide explains the main activities to consider before choosing an allowance.
Check your provider's app or account for three complete billing periods. Identify the busiest month that reflects your normal life, then account for anything new: a commute without Wi-Fi, a regular laptop connection or a move to a property with poorer broadband. Phone data counters help you spot heavy apps, but their reset dates may differ from your provider's billing cycle.
These ranges are practical editorial prompts, not official usage thresholds:
| Your highest representative mobile-data use | Sensible next comparison | Reason |
|---|---|---|
| Comfortably below 50GB | 50GB SIM deals or the full SIM finder | A 100GB+ plan may add little benefit unless it costs less or has better terms |
| Around 50–80GB | Start with current 100GB offers | There is potentially useful room for a busier month |
| Around 80–100GB | Compare 100GB with 150GB, 200GB and unlimited offers shown above | An unusual week could exhaust a 100GB bundle |
| Regularly over 100GB | Compare the next finite allowance that covers your peak, then unlimited SIMs | Repeated add-ons or slowdowns may make a larger plan preferable |
No range alone tells you which tariff wins: a 150GB plan on a better network or with a lower total bill may beat a 100GB plan even when both would cover your usage. Conversely, a heavy-data offer is not automatically good value just because its headline data figure is large.
Tethering is where a generous-looking phone allowance can suddenly feel small. Instead of relying on generic claims about how many hours of video 100GB buys, build a budget from your own phone use and the additional data you expect a laptop, tablet or second device to consume.
Consider this illustrative scenario, not measured typical usage:
| Planned use in one allowance period | Data budget |
|---|---|
| Ordinary phone use, excluding the proposed new laptop sessions | 45GB |
| Eight hotspot days with a self-set allowance of 6GB each | 48GB |
| Planned combined use | 93GB |
On a 100GB plan, that hypothetical budget leaves 7GB. A further 10GB of downloads or unexpected use would bring it to 103GB, over the cap. On a 150GB plan, the same 93GB budget leaves 57GB spare. This does not mean a working day uses 6GB; it shows how to test whether your own assumptions survive a demanding month.
Before choosing a phone SIM for regular tethering:
If you want a more detailed device-by-device assessment, see our hotspot and tethering guide. For a SIM installed in a tablet or router, the data-only SIM guide covers the separate compatibility decision.
The best-value 100GB+ deal is the cheapest suitable plan over the period you expect to use it—not necessarily the card with the largest data figure or the lowest first payment. Compare the following in order.
A short-lived discount can improve a deal, but it should never be mistaken for its regular price. The calculation below is hypothetical, not a quote from any provider on this page:
| Example high-data plan | Assumed twelve calendar-month payments | Total |
|---|---|---|
| A: introductory discount | £7 for three months, then £13 for nine months | £138 |
| B: steady price | £11 for twelve months | £132 |
Under those assumptions, B costs £6 less despite A's cheaper opening months. Add any upfront fees, scheduled price increases and realistic cashback conditions before declaring a winner. For a contract that renews every 30 days rather than by calendar month, also check how many actual payments fall within your comparison period.
Do not compare the minimum one-month cost of a rolling offer with the full 24-month obligation of a fixed-term offer as if they described the same commitment. Someone who may move or lose reliable coverage could rationally pay a little more for flexibility. If that matters, compare 30-day and no-contract SIM deals.
For new consumer telecoms contracts, Ofcom's price-rise rules prohibit inflation-linked or percentage-based increases written into the contract. Providers may still specify increases in pounds and pence upfront. Read the actual dates and monetary amounts rather than interpreting a low starting figure as a fixed-price promise.
Doubling an allowance from 100GB to 200GB halves the nominal price per gigabyte if the monthly price stays identical. That arithmetic is straightforward, but it does not mean you will use or benefit from the extra 100GB. A better comparison is the amount leaving your account for a plan with enough data, the coverage you need and an acceptable commitment.
Likewise, unlimited has no fixed gigabyte denominator. It can be the more economical choice if you repeatedly exceed capped bundles—but only after accounting for network performance, speed policies, acceptable-use conditions and total cost. If a 100GB plan and an unlimited plan cost about the same over the period you need, compare the minimum commitment too: a flexible 100GB plan may suit you better than a much longer unlimited contract. Unlimited UK data is not a guarantee of unrestricted speed, devices or overseas use. The dedicated unlimited comparison is the right route when you have already decided that a finite cap is unsuitable.
High-data promotions can add more gigabytes for a fixed window or on particular renewal terms. Check which allowance is contractual, when the promotion ends, whether the price also changes and what happens if you renew. A card showing a larger temporary data boost does not automatically make a smaller ongoing bundle equivalent to that larger tier.
| Your main use | Question to answer on the shortlisted tariff |
|---|---|
| Heavy phone streaming or downloads | Does the network perform reliably where you use it, and is there a plan-specific speed restriction? |
| Laptop hotspot or shared devices | Is tethering permitted for this use, and will all connected devices draw from the same allowance? |
| SIM in a tablet, MiFi or router | Is this a suitable phone SIM or a data-only product, and is your exact device supported? |
| Calls and texts on your main number | Does this plan include the voice and messaging services you need? Data-only products may not. |
| Travel outside the UK | What data and charges apply in the destination? UK 100GB or unlimited does not imply the same roaming allowance. |
Two points deserve particular care.
First, coverage and speed are different from allowance. Use Ofcom's Map Your Mobile to check predicted service where you live, work or travel, then review the provider's own coverage details. A map is not a guarantee of indoor reception, actual throughput or performance at a congested time. A 5G badge does not promise a specific speed. Providers sharing underlying network infrastructure can still differ in plan restrictions and services. If that capability is your priority, visit 5G SIM deals or eSIM deals.
Second, 100GB at home is not automatically 100GB abroad. Roaming may be excluded, purchased through a pass or limited by destination and fair-use conditions. An unlimited UK tariff can also have a finite roaming allowance. If travel is central to the decision, compare SIMs with EU roaming and verify the destination-specific terms at checkout.
Possibly for a light-use household or a temporary setup, but do not assume even a 100GB or 200GB phone SIM will cover a household's fixed-broadband habits. Several people streaming, downloading games, backing up files or using smart devices can exhaust a mobile allowance much faster than one person's phone use suggests.
The scale difference is worth seeing, without treating the two measurements as interchangeable. In its 2026 Communications Market Report, Ofcom reports an average 583GB per residential fixed-broadband connection in July 2025, including uploads and downloads. That is a different customer base, connection type and measurement period from its 11.8GB mobile-user figure. It is not a prediction for your home, but it illustrates why a mobile plan marketed as generous may be small for several connected devices.
If home broadband is unreliable or unavailable, compare larger fixed allowances with unlimited and dedicated mobile-broadband products. Before committing, check sustained signal at the actual property, router compatibility, acceptable-use terms, contract length and the cost of equipment. A great phone SIM price is not a reason to buy an unsuitable home connection.
Go back to the live offers above and shortlist two or three tariffs on networks that work where you need them. Compare the same planned period—not just the introductory payment—and look at the actual data allowance, permanent versus promotional extras, any speed or hotspot rules and the minimum commitment. Open Full plan details, then use the existing View Deal button to check the final provider terms and order.
If you are switching an existing UK mobile service and keeping your number, Ofcom's Text to Switch guidance explains how to text PAC to 65075 and pass the resulting code to the new provider. Check any early-exit charge before completing the switch. Buying an additional SIM without ending your current service does not require porting your number.
Yes. The current comparison includes finite allowances of at least 100GB and plans labelled unlimited in the live catalogue. If you want unlimited-labelled offers without finite bundles, use our unlimited SIM-only page. Always check the individual provider's use and speed terms.
No. The plus sign means 100GB or more. You may see other fixed-data tiers as well as unlimited. Read each live card's displayed allowance and confirm the plan at the provider; a temporary extra-data promotion may change.
It depends on the laptop's actual traffic. Web browsing may be modest, but video calls, synchronisation and downloads can make daily demand unpredictable. Add the laptop's expected usage to your own mobile usage, allow headroom and check tethering terms before relying on a 100GB plan.
No. Data-only services are intended primarily for connected devices and may not include normal UK calls or texts. A conventional phone SIM can also have restrictions on router use. Check the plan's intended use and your device's SIM or eSIM compatibility.
No. 100GB is a volume of data, not a speed. A faster connection can make downloads quicker and may lead you to stream at higher quality, but it does not enlarge the bundle. Check coverage and any tariff-level speed limits separately.
Do not assume so. UK data allowances, EU roaming benefits and any fair-use caps are separate plan conditions. Check the destination and the provider's current roaming schedule; the same warning applies to unlimited UK plans.
There is no permanent cheapest winner. Sort the current selected offers, then compare the amount payable over your intended period, including later rates and the minimum commitment. The lowest opening price need not produce the lowest total bill, and a different data tier may be better value.
Consumer guidance and official references checked on 19 October 2026. Tariff prices, promotional allowances, roaming terms, contract conditions and verification dates are supplied by the existing live DealPriceCheck catalogue and may change. Confirm the selected offer on the provider's website before purchasing.