United Kingdom · SIM-only
Compare selected UK unlimited data SIM-only deals using the live offers below. The cheapest first bill is not always the cheapest deal: check the price after a promotion, the minimum commitment, coverage and any speed or tethering restrictions. Unlimited UK data does not automatically mean uncapped 5G or unlimited roaming. Filter the plans, then confirm the exact terms with the provider before you buy.
These offers are selected from the live DealPriceCheck dataset. Open a deal to see its full terms, then use the final provider link only when it suits you.
No current offers match these filters.
The best-value unlimited SIM is the one that works where you use it and fits how long you want to stay. If your signal is poor at home, a lower price or a higher advertised speed will not fix it. If you might switch again soon, a discounted 24-month deal could cost more to leave than a flexible plan costs to keep.
| You mainly want… | Compare this first | Easy to miss |
|---|---|---|
| A low-cost unlimited SIM you'll keep | Full commitment cost, when a promotion ends and any scheduled rises | The headline price may last only a few months |
| The freedom to switch | Rolling or 30-day terms, renewal and cancellation rules | One period's charge is not the cost of a full year |
| Streaming and laptop tethering | Indoor coverage, speeds and permitted hotspot use | Unlimited GB will not fix a weak or restricted connection |
| Data while travelling | Included destinations, roaming allowance and charges | Unlimited UK data is not unlimited overseas data |
Use the live filters to narrow the choice: start with Network if signal is your priority, or Contract if flexibility matters most. Then use the 5G, eSIM or EU roaming options only if you need them. A filtered result is a shortlist of matching catalogue offers, not a ranking of the entire UK market.
Start with the network, not the brand. Use Ofcom's Map Your Mobile checker for the places that matter to you, including indoors. Its coverage and performance information is a guide, not a guarantee for a particular room, journey or phone. If your signal is good but your bill isn't, Keep My Signal on our SIM-only comparison page can help you find cheaper alternatives on the same underlying network. Sharing a network does not guarantee identical speeds, Wi-Fi Calling or other features.
A low advertised price can be a genuine bargain, but the cheapest first month and the cheapest contract are different things. Read the live card's monthly price, promotion details, contract length and, where shown, Minimum contract cost together. Some cards also show an Effective £/month figure calculated over the stated term. A rolling tariff may instead show Minimum term cost: that is not the price of keeping it for a year. These figures reflect the details recorded for that offer; they are not a guaranteed final checkout quote. If a card does not establish how a future rise applies, multiplying the starting price by the number of months gives only a base-price calculation.
Here is a deliberately hypothetical example, not an offer available on this site. Assume two 24-month SIMs have equivalent coverage and benefits, no upfront fees and no annual rises:
| Illustrative plan | Payment pattern | Cost over 24 monthly bills |
|---|---|---|
| Plan A: promotional | £10 for 6 months, then £22 for 18 months | £456 (average £19/month) |
| Plan B: flat rate | £18 every month | £432 (average £18/month) |
Plan A looks cheaper at the start but costs £24 more over the minimum term. Its first six months save £48 against Plan B, but its subsequent £4 monthly premium uses up that saving by month 18. That is why the point at which you might leave matters — although a 24-month contract may still charge you for ending it early. The comparison changes again if either real offer includes a different billing schedule, eligibility rule, fee or contractual increase. Do not confuse a displayed effective monthly cost over a commitment with the amount you can pay for one month and then leave.
Since January 2025, Ofcom's rules for new UK consumer contracts have required specified in-contract rises to be stated in pounds and pence before sign-up, with their timing made clear; inflation-linked or percentage-based rise terms are no longer permitted in new contracts. Read Ofcom's guide to telecoms price rises, then check the exact provider checkout and contract summary. A general network pricing policy does not establish the treatment of every listed deal.
If avoiding scheduled rises is a priority, compare SIMs with no annual price rises. No annual rise does not necessarily mean the promotional introductory price lasts indefinitely.
A longer commitment can make sense when you know the network works and its total required payments are worthwhile. A 30-day or monthly rolling offer may suit a temporary address, an untested network or someone whose circumstances may change. A lower locked-in rate is not automatically a better deal if you only need service for a short period.
Check exactly what “30-day”, “one-month” and “monthly” mean. Twelve prepaid 30-day periods cover 360 days, whereas a contract billed by calendar month follows different dates. Do not multiply every rolling plan by 12 — or automatically charge it for 13 renewals — without checking how that product bills and when you intend to cancel. Our 30-day versus 12-month unlimited SIM guide works through the timing and cost differences.
No. An unlimited UK-data allowance ordinarily removes the fixed monthly number of gigabytes found on capped plans. It does not guarantee the fastest possible connection. Some tariffs have a stated maximum speed; even one without a plan-level cap can slow at busy sites or in weak coverage. A “5G included” label means neither that you will get 5G everywhere nor that the tariff has no speed limit.
Two restrictions that sound similar can work very differently. A published 100Mbps maximum, for example, limits the plan's peak speed regardless of how many gigabytes you have used. A fair-use rule may instead permit slower service in specified circumstances after unusually high usage. Neither should be described as a hidden fixed monthly allowance without checking what the terms actually say.
Before paying extra for a premium unlimited tier, ask whether you would benefit from its speed. Someone mainly messaging and streaming on a phone may be content with a connection that would frustrate a household tethering several laptops. Check the exact plan's published cap, your phone's capabilities and real-world signal. For the distinction between 2Mbps, 10Mbps, 100Mbps and uncapped offers, see our UK SIM speed limits guide.
Possibly, but check the device rules first. Using your phone as a personal hotspot and putting a SIM into a dedicated 4G/5G router are not necessarily treated the same way. Occasional laptop access is different from running an entire home connection continuously. Check supported devices, tethering permissions, traffic management and any restrictions on business or permanent-router use before relying on a phone SIM as home broadband. If that is your main purpose, our hotspot and tethering guide goes into the device and usage questions.
An acceptable-use policy is not proof that every unlimited plan secretly has a fixed UK data cap. What matters is the actual restriction, when it applies and what happens to a legitimate customer. The ASA's guidance on unlimited telecoms claims explains why the impact and visibility of restrictions matter. Our guide to what “unlimited” really means covers fair use in more detail.
Not as an unlimited allowance by default. UK data and roaming are separate parts of the offer. An unlimited plan may include a smaller allowance abroad, charge for a pass, exclude a destination or apply a fair-use ceiling. Do not assume a published roaming allowance is extra data on top of your UK package, or that every country you might visit is included.
For frequent trips, look up your actual destination, any daily charge, the permitted roaming data and what happens after it runs out. If roaming matters more than a very large UK allowance, compare SIM deals with EU roaming rather than choosing purely on the word “unlimited”.
Unlimited is worth considering if mobile usage is genuinely heavy or unpredictable, especially for regular streaming or tethering away from Wi-Fi. It can also be convenient if worrying about a remaining allowance is itself a problem. But convenience has a price: if you usually stay well below a large fixed bundle, paying for unlimited may buy capacity you never use.
Open your network app or recent bills and check three ordinary months, including the highest one. Allow room for unusually heavy months and compare real-world coverage, contract length and the same expected period of ownership. You may find a suitable plan among our 100GB+ SIM-only deals. Don't assume a capped plan is always cheaper: promotions can reverse the result, so compare the live offers rather than a rule of thumb. For a fuller allowance calculation, see how much mobile data you need.
Use Full plan details for the information held in our catalogue, then View Deal to reach the provider. The final checkout and contract summary take precedence if an offer has changed. A brand offering eSIM generally does not mean every plan or purchase route supports it; compare eSIM-enabled deals if that is essential.
If you want to move to another UK operator and keep your number, text PAC to 65075 from your current line and give the code to the new provider. Unsure whether you are still in contract? Text INFO to 85075 to check your status, and review any early-exit charges before switching. See Ofcom's switching guidance or our step-by-step number transfer guide.
There is no permanent winner. Introductory prices, exclusive promotions and availability change, and the cheapest opening payment may not have the lowest full-term cost. Use the current catalogue above and compare like-for-like contract lengths, coverage and the payment schedule. DealPriceCheck lists selected providers, not every offer in the UK market.
It generally means no ordinary fixed monthly UK data allowance. It does not necessarily remove speed caps, permitted-use rules or fair-use measures, and it does not promise unlimited roaming. Read the terms of the specific plan.
Some do. A provider may publish a maximum speed such as 100Mbps, while another tier has different speed terms. Check the specific tariff, because “5G” describes a network technology, not a guaranteed download speed. A speed cap and a fair-use restriction are not the same thing.
Possibly, but confirm router or hotspot permission, indoor signal and the terms for prolonged heavy use. Unlimited data alone says nothing about the reliability of a permanent home connection.
Not automatically. A rolling plan can let you leave sooner; a longer plan can have a lower total cost if you stay. Compare charges over the same period, including renewals, any promotions and applicable rises, then consider early-exit flexibility.
No. Roaming allowances, eligible countries and charges are specific to the plan. A UK unlimited allowance is not an overseas unlimited allowance.
Yes. Some unlimited packages renew every 30 days or on a rolling monthly basis; others are prepaid. These are not necessarily the same as one-off pay-as-you-go credit. Check the payment and renewal dates, whether renewal is automatic, any cancellation notice and how introductory prices expire. Compare no-contract SIM options, then confirm the deal you choose actually includes unlimited data.