T-Mobile charges $25 to $50 per month for each additional line, depending on your plan and whether you bring your own phone

The cost to add a line to T-Mobile depends on which plan you already have and whether the new line needs a phone. On T-Mobile's standard plans, a new line costs $25 per month if you bring your own device, or $25 to $50 per month if T-Mobile provides the phone through a payment plan. If you are on an older T-Mobile plan, the price may differ — T-Mobile does not always charge the same rate for new lines on legacy plans.

The monthly charge is separate from any upfront costs. If you need a phone, T-Mobile spreads the cost over 24 months as an equipment installment plan. A budget phone might add $5 to $10 per month to your bill; a flagship phone can add $30 or more. You can also buy a phone outright at a retailer and bring it to T-Mobile, which avoids the installment plan but requires you to pay the full price upfront.

Key Takeaways

  • Adding a line to an existing T-Mobile account costs $25 per month for a line without a phone, or $25 to $50 per month if T-Mobile finances the device.
  • The phone cost is added separately as a 24-month installment plan, so a $600 phone adds roughly $25 per month on top of the line fee.
  • You can bring a phone you already own or buy one elsewhere and avoid the installment plan entirely.
  • T-Mobile's older plans may have different pricing for additional lines, so checking your current bill or calling customer service will show your exact rate.
  • Family plans and promotional offers sometimes reduce the per-line cost, so it is worth asking whether a discount applies when you add the line.

How the monthly charge breaks down

T-Mobile separates the line fee from the device cost. The line itself — the phone number, the network access, and the data allowance — costs $25 per month on most current plans. This is the same whether you use 100 MB or 100 GB of data, because T-Mobile's standard plans include unlimited data.

If T-Mobile provides the phone, that device cost is billed separately as an equipment installment. A phone that costs $240 at retail adds $10 per month for 24 months. A $600 phone adds $25 per month. You see both charges on your bill: the $25 line fee plus the device installment.

If you bring your own phone, you pay only the $25 line fee. This is the cheapest option if you already own a compatible device. T-Mobile's network works with most phones sold in the United States, but older or international phones may not work — you can check compatibility on T-Mobile's website by entering the phone's model number.

When the cost is higher or lower

T-Mobile's pricing changes based on what plan you have and what promotions are running. If you are on a family plan with four or more lines, T-Mobile sometimes discounts the per-line cost to $20 or less. If you are on an older plan from before T-Mobile's recent restructuring, the cost to add a line may be $30 or $35 instead of $25.

T-Mobile also runs periodic promotions that waive the line fee for a set period or discount the phone cost. These offers change monthly and are usually advertised in T-Mobile's app or on their website. Calling T-Mobile customer service before you add a line can reveal whether a current promotion applies to you.

If you are switching from another carrier, T-Mobile sometimes offers bill credits that reduce the cost of the new line or the phone. These credits are applied over several months and require you to trade in your old phone or meet other conditions — ask about trade-in value when you call.

Bringing your own phone versus financing one

If you own a compatible phone, bringing it to T-Mobile is the lowest-cost option. You pay only the $25 monthly line fee with no upfront cost and no installment plan. The phone must be unlocked (not locked to another carrier) and compatible with T-Mobile's network bands. Most phones sold in the United States in the past five years work on T-Mobile, but checking the model number on T-Mobile's website takes two minutes and confirms compatibility.

If you need a new phone, you have two choices: finance it through T-Mobile or buy it elsewhere. Financing through T-Mobile spreads the cost over 24 months, which can feel easier on your monthly budget but costs the same total amount as buying the phone outright. Buying a phone from a retailer like Best Buy, Amazon, or a carrier store and bringing it to T-Mobile costs more upfront but avoids the installment plan and gives you more phone choices.

Financing a phone through T-Mobile ties that device to your account. If you stop paying the installment plan, T-Mobile can suspend service on that line or report the debt to a credit agency. If you own the phone outright, you have no obligation to T-Mobile beyond the monthly line fee.

How to add a line and see your exact cost

You can add a line through T-Mobile's website, in a T-Mobile store, or by calling customer service at 611 from a T-Mobile phone or 1-844-839-4534 from any phone. Adding a line online takes about 10 minutes; in a store or by phone, it takes 20 to 30 minutes.

Before you add a line, ask T-Mobile what the total monthly cost will be. Tell them whether you are bringing a phone or need one financed, and ask whether any current promotions explore to your account. They can show you the exact line fee, the device installment (if any), and any promotional credits before you commit.

Once the line is active, it appears on your next bill. You can see the breakdown of charges in the T-Mobile app or on your online account — the line fee, the device installment, any taxes, and any promotional credits are all listed separately.

What happens if you cancel the line later

If you cancel a line within the first 14 days, T-Mobile refunds the line fee and any upfront costs. After 14 days, you can cancel anytime, but if you financed a phone through T-Mobile, you still owe the remaining balance on that device. If you owe $200 on a phone and cancel the line, you must pay that $200 to T-Mobile.

You can avoid the remaining device balance by trading in the phone to T-Mobile or another carrier. T-Mobile's trade-in value depends on the phone's condition and model — a two-year-old phone might be worth $50 to $150. If the trade-in value covers the remaining balance, you owe nothing. If it does not, you pay the difference.

Comparing T-Mobile's line cost to other carriers

T-Mobile's $25 per-line cost is competitive with other major carriers. Verizon charges $25 to $35 per line depending on the plan. AT&T charges $25 to $40 per line. Smaller carriers like Mint Mobile or Visible charge $25 to $45 per month for a full plan (not just a line added to an existing account), so the comparison depends on whether you are adding to an existing plan or starting fresh.

The real difference between carriers is not the per-line cost but what is included. T-Mobile includes unlimited data on all plans; Verizon and AT&T have plans with data caps. T-Mobile's network coverage is strong in cities and suburbs but weaker in rural areas than Verizon's. If you live or travel in rural areas, Verizon's higher cost may be worth it for better coverage.

Frequently Asked Questions

Can I add a line without a phone number?

No. Every line on a T-Mobile account has a phone number and is billed separately. If you want to add a device without a new phone number — for example, a tablet or smartwatch — you add it as a connected device to an existing line, not as a new line. Connected devices cost $10 to $15 per month and use the data from your existing line.

Do I have to sign a contract to add a line?

No. T-Mobile does not require contracts. You can cancel a line anytime after the 14-day return period, though you remain responsible for any remaining device balance if you financed a phone through T-Mobile.

What if I want to add a line but keep my current phone?

You can add a line and bring your own phone for $25 per month with no upfront cost. The phone must be unlocked and compatible with T-Mobile's network. Check compatibility on T-Mobile's website before you add the line.

Does adding a line increase my bill by exactly $25 per month?

Not necessarily. The line fee is $25, but taxes are added on top. If you finance a phone, the device installment is added separately. If a promotion applies, it may reduce the total. Your exact bill increase depends on your state's tax rate, whether you finance a device, and what promotions are active.

Can I add a line to a prepaid T-Mobile account?

T-Mobile's prepaid plans do not support multiple lines on one account. Each prepaid line is separate. If you want multiple lines, you need a postpaid account (the standard monthly billing plan), which costs $25 per line.