100GB vs Unlimited Data SIM: Which Is Better Value in the UK?

Choose 100GB if it comfortably covers your busiest normal month and the saving is meaningful. Choose unlimited if you often go over 100GB, rely on your phone for broadband or would otherwise keep paying for extra data. Before you decide, check 150GB and 200GB plans too. A bigger fixed allowance is often the better answer to the question "100GB or unlimited?"

You are buying usable data on a reliable UK network, not just a number of gigabytes. A cheap unlimited SIM with tight speed rules or a long commitment can be less useful than a fast, flexible 100GB plan. A discounted unlimited deal can also cost less overall than a badly priced 100GB contract. To compare them fairly, look at your own usage, the full payment schedule and what happens when you hit the limit.

To see today's options, compare 100GB+ UK SIM deals and unlimited data SIM deals. Both pages use DealPriceCheck's live offer cards, and each card's View Deal button takes you to the provider's checkout.

100GB vs unlimited at a glance

• 100GB is approximately 3.3GB per day over 30 days — an average, not a daily cap.
• Look at your highest realistic usage period, not only the average.
• 100GB, 150GB, 200GB and unlimited can all be sensible choices. The best-value tier may lie between the two extremes.
• At one provider's 22 October 2026 prices, moving from 100GB to 150GB cost £2.50 extra per 30-day renewal; moving to unlimited cost £10 extra.
• Running out can be expensive where out-of-bundle data is charged by the megabyte. Check your specific SIM's overage and auto top-up rules.
• Unlimited UK data is not automatically unlimited in the EU, and unlimited does not necessarily mean uncapped speed.

The deciding question: how close do you get to 100GB?

These are decision ranges, not official usage thresholds. Someone who always uses 92GB might manage fine on 100GB. Someone who averages 60GB but needs 160GB during regular trips could find it too tight. Use your highest realistic month, not just an average.

A like-for-like price test: 100GB, 150GB, 200GB or unlimited

Setting a promotional 24-month deal from one operator against a flexible plan from another can make either allowance look cheap. For a cleaner example, compare four 1pMobile bundles. All run on the EE network, renew every 30 days and include unlimited standard UK calls and texts.

This is an official, dated product snapshot checked on 22 October 2026. It is not a permanent price list or a live DealPriceCheck rate.

The most useful comparison is often 100GB versus 150GB: 50GB more for £2.50 extra each renewal in this specific range. Another £2.50 takes the allowance to 200GB; another £5 takes it to unlimited. Compared with 100GB, unlimited costs £10 more per renewal, or £120 across twelve renewals at these snapshot prices.

Twelve 30-day renewals cover 360 days, not a 365-day year. Continuous service beyond day 360 would normally trigger a thirteenth renewal; that payment also buys a further 30-day period. The figures above are illustrations of twelve renewals, not guaranteed year-long bills.

An upfront yearly Boost changes the comparison. In the same 22 October 2026 snapshot, 1pMobile also published a separate 1-year 100GB Boost at £165, providing 100GB every 30 days, and a 1-year unlimited Boost at £275, paid upfront. Those totals differ from £180 and £300 for twelve rolling payments, but a one-year prepaid product and twelve 30-day renewals do not have identical duration, payment timing or flexibility. If you can pay in advance, compare the annual Boost terms too, rather than calling the rolling table the cheapest 1pMobile option. Use DealPriceCheck’s 1pMobile page for live rolling deals and the approved affiliate products link below for the operator’s separate annual range.

There is one important operator-specific catch. 1pMobile's published unlimited fair-use policy says speeds may be slowed at busy locations after more than 500GB in a Boost period. That is not a hard 500GB allowance, but it shows that unlimited does not promise the same performance at every level of use. Its higher-allowance Boosts also have a separately published 14GB EU roaming cap, so unlimited UK data does not give you unlimited data abroad.

Where to buy: compare live 1pMobile plans on DealPriceCheck for the 100GB, 150GB, 200GB and unlimited offers and their existing Awin View Deal routes. You can also browse 1pMobile's current SIM products through our affiliate link. That link opens the general products page, not a direct checkout for a particular bundle.

This is a like-for-like example, not a claim that 1pMobile is cheapest for everyone. DealPriceCheck's 100GB+ live catalogue covers other networks, and unlimited offers may cost less on different terms. Compare them before you buy.

The most expensive mistake: running out of 100GB

The right comparison is not always £15 against £25. It can be £15 plus excess data against a larger bundle that would have covered your month.

1pMobile's published 100GB terms say data beyond the allowance is charged 1p per MB and deducted from account credit, or you can purchase another data Boost. The provider also describes automatic £10 credit top-ups when the usage balance falls below £2. That makes overage worth checking before a high-data month, not after a surprising bill.

At that rate, 250MB extra costs £2.50 in usage charges. This is the same as the snapshot £2.50 difference between the 100GB and 150GB Boosts for a whole 30-day renewal. A £10 automatic credit top-up is a wallet payment, not an additional £10 fee for using 250MB; unused credit may remain available. Approximately 1GB outside the bundle would cost around £10 at 1p/MB, subject to measured units and charging. This is a useful break-even illustration, not a guarantee that a plan can be upgraded mid-cycle, that old credit will be refunded or that every operator charges for excess data. If you can anticipate the need, check the next-renewal upgrade or extra Boost options first.

Other providers may stop data, restrict it or offer a different top-up product instead. Compare each plan's actual rule.

Before choosing 100GB, find out whether excess data stops, costs extra or slows down. Check the credit balance and auto top-up settings, then compare 150GB, 200GB or an extra data Boost for your next high-use period. Do not assume a provider changes your current renewal automatically.

A cap is not a problem in itself. A predictable cap with cheap or controllable overage can save you money. An opaque overage rule on a plan you regularly use up is a sign to move up.

How much can 100GB actually do?

Over a 30-day period, 100GB is roughly 3.3GB a day on average. It is not normally a daily quota. You can use more on one day and less on another until the period's total runs out.

Video quality and time away from Wi-Fi matter more than labels like "heavy user". Netflix's official data-usage guide lists up to 3GB an hour for HD and up to 7GB an hour for Ultra HD/4K at its high-quality setting. On those assumptions:

These are worked illustrations, not universal streaming rates or forecasts. Mobile apps can use different compression, playback and data-saving settings, and your allowance also has to cover everything else. On home Wi-Fi, video normally uses your broadband, not your SIM's mobile data. On a train or through a phone hotspot, it usually counts against the SIM allowance.

Other less obvious uses include laptop software updates, cloud photo backups, video calls, game downloads and tethered devices that upload files automatically. Online multiplayer itself can use much less data than downloading the game or its updates, so don't buy unlimited just because you play games without checking your real usage.

If you can't estimate an allowance from experience, start with how much mobile data you need. This guide is the next step: does paying for more than 100GB actually improve your deal?

Your busiest month matters more than your average

Open your current mobile account and note the data used in each of your three most recent complete allowance periods. Use the operator's records where you can, because your handset counter may reset on a different day from your billing cycle. Then make one adjustment for any likely change in routine, such as more commuting, a house move, less Wi-Fi, a new job or a planned broadband outage.

Take two people who both average 75GB across three periods:

Neither example proves unlimited is cheaper. For the second person, a 200GB bundle or a temporary upgrade may make more sense than paying for unlimited all year. But an occasional 160GB month is a real buying constraint that a comforting 75GB average hides.

If your provider's dashboard can't show past months, watch one complete billing period before you sign a long commitment. While you test, use your phone as you normally would. Don't deliberately cut your data to fit a deal.

When does unlimited become worth it?

You tether a laptop for work

Regular hotspot use can turn a manageable phone allowance into unpredictable multi-device use. Video meetings and document syncing are only part of it, since a laptop may download large updates when you least expect it. If you often go over 100GB across your phone and connected devices, unlimited may cut interruptions and extra charges.

Check your SIM's hotspot permission, speed restrictions and supported devices first. Unlimited data on a handset does not prove that a particular router or home installation is allowed under the same terms. Our tethering and hotspot guide covers the device and router decision; this article focuses on whether paying for extra GB makes sense.

You use mobile data instead of home broadband

If your SIM is the main connection for streaming, work, backups and several people, unlimited deserves serious thought. Even then, first check how the network performs indoors and during evening congestion. A usable broadband replacement needs sustained reliability, not just a large allowance. A dedicated home or mobile broadband service may suit multi-device use better.

Your monthly usage is close to the cap

If you reach 90 to 100GB most months, a 100GB plan gives you very little headroom. If unlimited costs only slightly more on otherwise comparable terms, not having to watch your usage may be worth it. If the price gap is large, 150GB or 200GB is the obvious middle option.

You simply want peace of mind

Peace of mind is a fair reason, but put a price on it. Ask whether you would pay the extra cost per renewal to stop monitoring your data or buying top-ups. If your biggest month was 42GB, a smaller plan could give you the same comfort with a generous margin and a lower bill.

Can a 100GB SIM be better than an unlimited SIM?

Yes. A data allowance and a connection's speed are separate features. A 100GB tariff with a higher permitted maximum speed and strong local reception can be more useful than an unlimited tariff with a low speed cap or poor signal. Both can say "5G" without delivering equal real-world performance.

Check four things on the cards you might buy:

For a first coverage check, use Ofcom's Map Your Mobile. It shows predicted local coverage and measured district-level performance, but neither guarantees your connection inside a particular building. For EE-based options, see our 1pMobile provider comparison and Lyca Mobile deals. Sharing EE infrastructure does not guarantee identical speeds, features or priorities. Our guide to how MVNO coverage and speeds compare explains why. For the separate question of whether unlimited allowances have hidden restrictions, read is unlimited mobile data really unlimited?.

A cheaper unlimited plan is not automatically the better deal

An unlimited plan with a lower first payment than a 100GB plan does not mean it costs less overall. Compare the whole price schedule.

Operators often advertise a low rate for an introductory period, with the regular rate applying afterwards. Instead of writing today's promotional price into an evergreen comparison, work it out like this:

Total cost over the chosen comparison period = the sum of scheduled payments at their actual rates (including disclosed price rises) + upfront charges + necessary extras.

Compare that with the total cost of a suitable 100GB, 150GB or 200GB plan over the same period, and note whether either option locks you in for much longer.

Don't confuse a 30-day renewal with a calendar-month bill. Twelve 30-day renewals cover 360 days. A 12-month minimum contract and a plan that renews every 30 days are not interchangeable, and a discounted 24-month plan should not be set beside one payment on a flexible SIM as if the commitment were the same. Ofcom requires specified contractual price rises on new contracts to be shown in pounds and pence before you sign up. Its guidance on price rises explains how this works.

For a deeper look at commitments, see 30-day versus 12-month unlimited SIMs. This guide helps you decide which data allowance you need before you pick a contract.

What should you compare on DealPriceCheck?

Start with the 100GB+ deals catalogue. It includes 100GB, higher fixed allowances and unlimited options, so don't read the category name as "exactly 100GB". Filter for a network and term you can accept. Compare the ongoing price and any introductory schedule as well as the gigabytes.

Then open unlimited SIM deals to compare plans with an unlimited UK allowance. Use Full plan details to review the selected offer, then View Deal for its purchase route. Those are existing catalogue functions; this guide does not need a second static product listing.

Two partner paths are worth checking alongside the wider market:

• 1pMobile on EE: compare its live 100GB, 150GB, 200GB and unlimited options or browse the operator's products through our Awin link. The second link goes to a product list, not a preselected package.
• Lyca Mobile on EE: compare Lyca's live UK SIM deals and explore its cheap SIM-only range through our Awin link. Check the exact deal, especially whether a promotional unlimited option has a 24-month minimum term and a different price after the introductory period. The affiliate destination is a general range, not a guaranteed checkout for one unlimited plan.

Neither brand wins just because it is a DealPriceCheck partner. A non-partner offer can fit your network, budget or contract better. The right deal gives you enough data at the lowest sensible total cost, not the one that pays the biggest commission.

The decision after the comparison

If your highest normal month is around 60 to 75GB and network performance is acceptable, a competitively priced 100GB SIM is a strong starting point. If you use 80 to 110GB, check 150GB and 200GB plans, your overage terms and the price gap to unlimited before you commit. If you regularly need more than 200GB, run a laptop hotspot daily or rely on mobile internet as home broadband, unlimited becomes more attractive — subject to speed, fair-use and device rules. If you use 150 to 200GB consistently, a correctly priced 200GB plan may still be the best deal.

Whatever the allowance, don't pay a premium for gigabytes while ignoring a weak signal or a contract you can't comfortably leave. Compare the actual provider and plan, not just the word "unlimited".

Questions about 100GB versus unlimited data

Is 100GB enough for a month in the UK?

Often, yes, including for many people who stream and use social media regularly. Check your actual off-Wi-Fi use in your busiest complete billing period. Heavy mobile video, downloads or tethering can make 100GB restrictive, while heavy use on home Wi-Fi may mean you need far less.

Is 100GB the same as unlimited data?

No. 100GB is a fixed allowance for the stated renewal period. Unlimited normally removes a conventional UK data cap for eligible use, but it can still carry speed, fair-use, tethering and roaming conditions.

How much more does unlimited cost than 100GB?

It depends on the provider and the deal. In a dated 22 October 2026 snapshot of 1pMobile's range, unlimited cost £10 more per 30-day renewal than 100GB (£25 versus £15), while 150GB cost only £2.50 more (£17.50 versus £15). Twelve such renewals of unlimited would cost £120 more than twelve renewals of 100GB. Check the live cards for current prices.

Is 150GB or 200GB a better choice than unlimited?

Often. If you go beyond 100GB but remain within 150GB, look at 150GB first. If you regularly need between 150GB and 200GB, compare 200GB with unlimited. At 1pMobile's dated snapshot prices, 150GB is £7.50 less and 200GB is £5 less per 30-day renewal than unlimited. Actual offers from other networks may have different gaps, speeds and commitments.

How many hours of Netflix can I watch on 100GB?

At Netflix's published maximum rates, about 33 hours of HD (up to 3GB an hour) or about 14 hours of 4K (up to 7GB an hour), if nothing else used the data. Mobile apps and data-saving settings can change these figures, and real use is often lower.

Is unlimited faster than 100GB?

Not by definition. Maximum speed, congestion, signal quality and plan rules decide performance. A 100GB SIM can be faster than an unlimited one, so check the particular tariff instead of assuming a bigger allowance means faster 5G.

What happens if I use all 100GB?

It depends on the provider. Data might stop, slow down, trigger an extra-data purchase or be charged outside the allowance. Under 1pMobile's published 100GB terms, excess data can use account credit at 1p/MB and auto top-ups may apply; other operators have different rules. Check before a big download.

Is 100GB enough for a laptop hotspot?

It can be for occasional work. Frequent video meetings, downloads and background laptop updates may use much more. Check your combined usage and the SIM's tethering and device terms before you rely on it.

Does unlimited UK mobile data include unlimited EU roaming?

No. Roaming can have a separate fair-use allowance or charges, even on unlimited UK plans. For example, 1pMobile publishes a 14GB EU roaming cap on the relevant larger Boosts, including its unlimited option.

Can I switch to unlimited later?

Many flexible bundles let you change at renewal, but the rules vary. On a long minimum-term contract, upgrading or moving down may be restricted or costly. Check the provider's plan-change policy before you assume you can switch freely.

Bottom line: measure your busiest month, find out what going over 100GB would cost, compare 150GB and 200GB middle options and only then compare the best available unlimited deal. Your network, renewal period and total price matter as much as the allowance.

DealPriceCheck compares selected UK SIM providers and may earn commission from qualifying partner links. Product availability, data allowances, excess charges, fair-use terms, promotions and prices can change, so check the exact provider offer before you buy.