About the Phone Plan Cost Calculator
Cell phone plans are hard to compare because the monthly price is only part of the cost. A premium unlimited plan may bundle a “free” phone through monthly bill credits, while a prepaid or budget carrier charges far less each month but expects you to buy or bring your own device. This phone plan cost calculator puts two options side by side over the same period so you can see which is really cheaper.
For each plan, enter the monthly service price for all lines, the phone cost per line (whether you pay upfront or through installments), one-time activation or setup fees, and any monthly promotional or trade-in credits. Add the number of lines, the comparison period and the taxes and surcharges your carrier adds to the bill.
Use a period that matches the device installment or promo term — usually 24 or 36 months — because bill credits typically stop if you leave early. The calculator assumes 0% device financing, which is common on carrier installment plans.
With the default inputs, the you save with the cheaper plan is $2,271.60. Change any value above to recalculate instantly.
How to use the phone plan cost calculator
- 1Enter the number of lines and a comparison period that matches the device or promo term.
- 2Enter your typical taxes and surcharges as a percentage of the service price.
- 3Fill in Plan A’s monthly price, phone cost per line, one-time fees and monthly credits.
- 4Repeat for Plan B — enter 0 for phones if you will keep your current devices.
- 5Compare the totals and effective monthly cost to see which plan is cheaper.
Formula and method
Each plan’s total cost over the period is the monthly service charge plus taxes and surcharges, multiplied by the number of months, plus the full price of the phones for every line, plus one-time activation or setup fees, minus any monthly bill credits. Dividing by the number of months gives an effective monthly cost that is directly comparable between plans, and dividing again by lines gives the cost per line.
The phone cost is the device’s full price whether you pay it upfront or in 0% installments, because installment plans spread the same amount over the term. If your carrier charges interest on device financing, add it to the phone cost. Taxes are applied to the service charge only.
- tax%
- Taxes, regulatory fees and surcharges as a % of the service price
- credits
- Monthly promotional, trade-in or autopay credits
Worked examples
Big-carrier unlimited with new phones vs budget plan with cheaper phones
Plan A’s $140 service plus 12% tax is $156.80 a month, or $3,763.20 over 24 months; adding two $800 phones and $70 in fees and subtracting $480 of credits gives $4,953.20. Plan B costs $1,881.60 in service plus $800 for two phones, or $2,681.60 — $2,271.60 less.
Bring your own phone to prepaid vs keep your current postpaid plan
With taxes included in the price, staying on a $75 plan costs $900 over a year. Switching to a $30 prepaid plan with a $15 SIM fee costs $375, saving $525 — about $31.25 a month effective cost on the new plan.
Family of four: free phones via 36 months of credits vs bring your own
Plan A’s service with tax totals $7,920, phones $3,320 and fees $140, less $3,312 of credits, for $8,068 (about $56 per line per month). Keeping current phones on a $160 plan costs $6,336 with tax, so it saves $1,732 over three years — but Plan A ends with four new phones.
Frequently asked questions
How do I compare cell phone plans fairly?+
Compare the total cost over the same period, including taxes and fees, the full price of any phones, activation fees and bill credits. Dividing that total by the number of months gives an effective monthly cost you can compare across carriers.
Are “free phone” deals really free?+
Usually the phone is paid off through monthly bill credits that last 24 to 36 months and often require a premium plan. If you leave early, the credits stop and the remaining device balance becomes due, so the phone is only free if you stay the full term.
Is prepaid cheaper than postpaid?+
Prepaid and budget carriers are often much cheaper per month, especially if you bring your own unlocked phone. Postpaid plans can win when big trade-in credits or multi-line discounts apply, which is exactly the trade-off this calculator measures.
How much do taxes and fees add to a phone bill?+
It varies widely by state, city and carrier: US bills can carry federal, state and local taxes, a Universal Service Fund charge, 911 fees and carrier “regulatory” surcharges. Some carriers and most prepaid brands include them in the advertised price. Divide the extra lines on a recent bill by the plan price to get your own percentage.