T-Mobile Fiber's new 5 Gig plan became available on Tuesday, November 3, at $90 a month with AutoPay, and it carries the only price guarantee left in the lineup: 10 years. On T-Mobile's new plan chart, the 300 Mbps, 1 Gig and 2 Gig tiers show no price guarantee at all.
That turns a decade of fixed pricing into a reason to buy the most expensive plan. When T-Mobile launched fiber nationally in June 2025, every tier came with a five-year guarantee. So the question for a new customer has changed: not only how much speed the house needs, but whether a locked price is worth paying extra for.
What T-Mobile Fiber 5 Gig costs and what the 10-year lock covers
The plan costs $90 a month with AutoPay, plus taxes and fees, according to T-Mobile's announcement. For a limited time, new 5 Gig customers also get two months free through bill credits and $300 in virtual prepaid cards within 14 weeks.
Upload and download speeds are symmetrical, and the plan includes a Wi-Fi router, a mesh extender for homes that need one, professional installation and unlimited data. There is no annual contract, and you do not need a T-Mobile phone line to get the advertised price.
The guarantee locks the price of the internet service itself from the day you sign up. Taxes and fees, voluntary equipment or speed upgrades, select limited-time promotions, per-use charges, third-party services and network management practices sit outside it. In practice, the $90 is fixed while the total on your bill can still move.
How T-Mobile's fiber price guarantee shrank from every plan to one
At the June 2025 launch, all three standard plans carried a five-year guarantee, and a limited-time Founders Club offer put a 10-year lock on 2 Gig for $70. Standard prices were $75 for Fiber 500, $90 for 1 Gig and $105 for 2 Gig with AutoPay, or $15 less with a T-Mobile voice line.
The new lineup is cheaper across the board. Fiber 300 is $45, 1 Gig is $60 and 2 Gig is $70 with AutoPay, and limited-time discounts bring the first two down to $35 and $55. None of the three comes with a price guarantee.
That leaves 5 Gig in an unusual position. At $90, it costs $15 less than 2 Gig did at launch without a phone line, and it is the one plan whose price T-Mobile promises to hold for a decade. Picking 2 Gig instead saves $20 a month today, but without any promise about the years after.
Can your home network actually use a 5 Gig fiber connection?
T-Mobile pitches 5 Gig as room for more people and devices online at once, rather than as speed for a single laptop. That distinction matters, because a computer on a standard Gigabit Ethernet port tops out at 1 Gbps, however fast the line coming into the house is.
To push more than that to one machine, the device and the router both need multi-gig ports, and the cabling has to keep up. A Cat 6 Ethernet cable handles 2.5 and 5 Gbps on full-length runs. T-Mobile has not said which router ships with 5 Gig, though its 2025 plans came with a Wi-Fi 6 model.
Where 5 Gig earns its price is the busy household, with several streams, a game download, video calls and security cameras all running at the same moment. Symmetrical upload is the part that sets fiber apart from cable and 5G home internet, and it is what cloud backups and camera feeds lean on.
What current T-Mobile Fiber customers should check before switching
The announcement does not say whether existing fiber customers can move to 5 Gig, or what happens to a five-year guarantee from 2025 if they do. The 10-year terms also leave voluntary speed upgrades outside the guarantee, so ask T-Mobile how a plan change affects your current price before switching.
The plan is limited to select locations, so the first step is entering your address at Fiber.T-Mobile.com. If 5 Gig shows up there, the decision comes down to one figure: $20 a month more than 2 Gig buys 10 years of a price that does not move.
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