Carrier deals spread the phone cost into the monthly bill, which can hide a high price. Buying the phone and pairing it with a low-cost or prepaid plan is often cheaper over two years – and leaves you free to switch.
How to use the Cell Phone Plan Calculator
- Contract length
- Phone price
- SIM-only plan (monthly)
- Carrier plan with phone (monthly)
- Upfront cost of the carrier deal
- Interest rate on savings
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the contract length, the phone price, the SIM-only monthly plan, the carrier’s monthly plan with the phone, any upfront fee and the interest rate on savings.
Tips
- Use your real spending from bank statements rather than guesses.
- Automate savings so they happen before you spend.
- Revisit your plan once a year or after any big life change.
- Keep an emergency fund before investing for long-term goals.
Common mistakes to avoid
- Underestimating irregular expenses such as car repairs, gifts and annual bills.
- Ignoring inflation for long-term goals.
- Taking on high-interest debt to fund wants.
Inputs explained
| Field | What to enter |
|---|---|
| Contract length | In months |
| Phone price | Amount in your currency |
| SIM-only plan (monthly) | Amount in your currency |
| Carrier plan with phone (monthly) | Amount in your currency |
| Upfront cost of the carrier deal | Amount in your currency |
| Interest rate on savings | In % |
What each result means
- Total cost – buy the phone outright = [Phone price] + [SIM-only plan (monthly)]×[Contract length] + [Phone price]×((1 + [Interest rate on savings]÷1200)^[Contract length] – 1)
- Total cost – carrier contract = [Carrier plan with phone (monthly)]×[Contract length] + [Upfront cost of the carrier deal]
- Difference = abs([Total cost – buy the phone outright] – [Total cost – carrier contract])
- Interest forgone on the phone price = [Phone price]×((1 + [Interest rate on savings]÷1200)^[Contract length] – 1)
Formula
Buy outright = phone price + SIM-only plan × monthsCarrier contract = monthly carrier plan × months (+ upfront cost)Interest forgone on the phone price = price × ((1 + r/12)^months − 1)Worked example
Inputs — Contract length: 24 months; Phone price: $900; SIM-only plan (monthly): $25; Carrier plan with phone (monthly): $75; Upfront cost of the carrier deal: $0; Interest rate on savings: 4 %.
Results — Total cost – buy the phone outright = $1,574.83; Total cost – carrier contract = $1,800.00; Cheaper option = Buy the phone outright; Difference = $225.17; Interest forgone on the phone price = $74.83.
Frequently asked questions
Is it cheaper to buy a phone outright?
Usually, over 2 years, if you pair it with a low-cost plan.
What is a SIM-only plan?
A plan without a phone – you bring your own device.
Do carrier deals include interest?
Often 0% financing, but the plan price may be higher.
What formula does the Cell Phone Plan Calculator use?
Buy outright = phone price + SIM-only plan × months.