SIM-Only vs Contract Calculator
Total cost comparison of SIM-only plus owned phone vs mobile contract.
Compare SIM-only plus an owned phone against a mobile contract over 2 years — see which is cheaper at total cost including the device.
What this tool does
This calculator compares the total financial outlay of two mobile phone strategies over a set period. It takes your SIM-only monthly cost, the upfront price of a phone you own separately, the monthly cost of a bundled contract, and your contract length, then calculates the combined expenses for each approach. The result shows the 2-year total cost of ownership under both options, revealing which path involves lower cumulative spending. The calculation does not account for differences in coverage, data allowances, handset upgrades, early termination fees, or resale value of your phone. It provides a straightforward cost comparison for educational illustration and assumes consistent monthly charges throughout the period.
Enter Values
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Formula Used
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Calculations or display — let us know.
Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
SIM-only plus buying phone outright is almost always cheaper than a mobile contract over the contract period. Contract 40/month × 24 months = 960. SIM-only 15/month × 24 = 360, plus 600 phone = 960. Identical in this example. But SIM-only commonly 10-15/month for equivalent data, making it 240-360 total — dramatic saving.
Contracts appeal because they split the device cost into monthly payments and feel 'free'. The math rarely supports them for anyone who could buy outright or finance cheaper. Exceptions: very specific premium phones on exclusive deals, or customers who genuinely couldn't afford lump sum.
How to use it
Input SIM-only monthly cost, phone purchase price (outright), contract monthly cost, and contract length in months. The tool shows total cost of each option.
What the result means
SIM-only total is monthly × contract length + phone price. Contract total is monthly × length. Winner is lower total. SIM-only saving shows the explicit saving from the cheaper route.
Quick example
With sim-only monthly of 15 and phone purchase price of 700 (plus contract monthly of 40 and contract length of 24), the result is Contract. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.
Which inputs matter most
You enter SIM-Only Monthly, Phone Purchase Price, Contract Monthly, and Contract Length. Two inputs usually tip the answer one way or the other. Identify which ones matter most by flipping each value past a round threshold and watching whether the option with the lower calculated total changes.
What's happening under the hood
SIM total is monthly × months + phone price. Contract total is monthly × months. Winner is lower total. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.
What the bill doesn't show
Standing charges, discounts, and usage tiers all blur the effective rate. The calculation here backs out the total so you're comparing apples to apples across providers, regardless of how each one packages the price.
What this doesn't capture
Usage varies month-to-month; tariffs change; discounts come and go. The figure here is a clean baseline — your actual annual bill will fluctuate around it. Use the calculation to benchmark providers, not as a prediction of a specific bill.
Comparing a £700 phone with £15 monthly SIM-only to £40 monthly contract over 24 months months shows Contract in total costs.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
The calculator computes the total cost of a SIM-only arrangement by multiplying the monthly SIM-only fee by the contract length in months, then adding the upfront phone purchase price. The total cost of a mobile contract is computed by multiplying the monthly contract fee by the contract length. The calculator then compares both totals and identifies the lower-cost option. The model assumes a constant monthly rate throughout the contract period with no price changes, fee increases, or mid-contract adjustments. It does not account for device insurance, accessory costs, early termination fees, network quality differences, or any variations in usage that might affect total value. The comparison treats both arrangements as simple linear costs over the stated timeframe.
References
Frequently Asked Questions
Why are contracts so much more?
What if I can't afford phone upfront?
Are there any contract advantages?
What SIM-only rate is good?
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