Mobile · Head to head
O2 vs Vodafone SIM-only: which costs less?
The quick answer
On 27 Oct 2026, O2's best-value deal is 100GB Classic Plan at £22.50 a month real cost and Vodafone's is 1GB at £18.50. Vodafone is cheaper by £4.00 a month on its best-value deal, with fees and stated price rises counted.
Best value from each 27 Oct 2026
11 deals · best value first
Every deal from both, ranked by real cost
Ranked by real cost: setup fees and every stated price rise in, reward cards out. Prices checked on each provider's own site, 27 Oct 2026.
Leaving early
What it costs to leave each one early
Leaving O2 early
SIM-only and Standard Plan contracts: monthly tariff cost x months left in the Minimum Period, minus 4% for early payment (VAT included). O2 Refresh: no charge on the airtime plan; the device plan must be paid off.
O2's own example: 12-month contract at £21 a month, leaving after six months = 6 x £21 = £126.00, less 4% = £120.96.
Notice: 30 days' notice (via My O2 or by contacting O2).
Leaving Vodafone early
Remaining monthly charges for the months left (after any discount), minus 2% for paying in one go. Device plan is separate and must keep being paid or be settled.
Vodafone's own example: £45 a month less £10 discount = £35 x 6 months = £210, less 2% (£4.20) = £205.80.
Notice: not stated on this page
From Vodafone's own page, read 26 Oct 2026
The big difference
The biggest difference is the network. O2 runs its own 4G and 5G network, while Vodafone SIM-only plans run on the Vodafone network, part of VodafoneThree. Both include 5G, and both list 24-month plans in our table.
Both include EU roaming in our table. Vodafone's roaming covers 52 European destinations with a 25GB allowance. Check the roaming allowance on each plan before you travel.
Since 17 January 2025, Ofcom rules require any price rise in a new contract to be stated in pounds and pence. Percentage and inflation-linked rises are banned in new contracts. Vodafone states its mid-contract rises in pounds on its deal page, and our table builds them into the real cost.
Sort the cheapest SIM-only deals by real cost to see which plan costs less overall.
Choose O2 if
O2 fits if you want its own network, EU roaming included and lots of data.
- You want its own network. O2 runs its own 4G and 5G network, and its SIM-only plans include 5G.
- You use your phone in Europe. EU roaming is included on O2 plans in our table.
- You want a big data allowance. O2 plans run from 100GB to unlimited, and fair usage applies. The offer price ends 4 November 2026. See O2 SIM-only plans.
Choose Vodafone if
Choose Vodafone if you want the Vodafone network, a small data plan or roaming across Europe.
- Small data needs: Vodafone plans start at 1GB, while O2 plans start at 100GB. Light users can pick a smaller allowance instead of paying for data they never use.
- Roaming in Europe: Vodafone lists inclusive roaming in 52 European destinations, with 25GB included. Handy for a holiday in one of those destinations.
- Unlimited calls and texts: Vodafone lists unlimited minutes and texts, plus a maximum download speed of 100Mb. Sort the table by data allowance to find the plan that suits you.
Straight answers
Questions people ask
- Is O2 cheaper than Vodafone?
- We rank O2 and Vodafone SIM-only deals side by side by real cost, so the cheapest one sits at the top of our table. Real cost adds up every monthly price, every price rise the provider has stated in pounds, and any setup fee, then divides the total by the number of months. See the lowest real cost today on our cheapest SIM-only deals page.
- What network do O2 and Vodafone use?
- O2 uses the O2 network, and Vodafone uses the Vodafone network. O2 runs its own 4G and 5G network, and its SIM-only plans include 5G. Vodafone is part of VodafoneThree, the merged Vodafone and Three UK business, and its SIM-only plans include 5G too.
- Can I switch from Vodafone to O2 and keep my number?
- Yes, you can keep your number when you switch from Vodafone to O2. Text PAC to 65075 to get your PAC code. Give that code to your new network, O2, when you sign up. Your number moves across in one working day.
Keep comparing
Your next question, answered
- O2 SIM-onlyEvery O2 SIM-only plan we track: data, contract, network and the real cost after stated price rises, read from O2's own site daily.
- Vodafone SIM-onlyEvery Vodafone SIM-only plan we track: data, contract, network and the real cost after stated price rises, read from Vodafone's own site daily.
- Cheapest SIM-onlyThe cheapest SIM-only deals on every UK network, by real cost after stated price rises. 30-day and contract plans, checked daily.