Carrierlytics City Coverage Guide

Diamond Bar, CA Cell Phone Coverage Map & Network Rankings (2026)

Don't overpay for a network that struggles where you actually use your phone.

Using FCC mobile coverage data across Diamond Bar, CA ZIP codes, Carrierlytics compares the top-performing networks and the cheapest plans that use them.



Cell phone coverage map for Diamond Bar, CA

Zoom in for local detail. Tap or click a colored area to see coverage and signal details. On mobile, use two fingers to move the map.

Coverage Key
Less covered More covered
Darker areas mean the carrier covers more of that location.

Map data © OpenStreetMap contributors, © CARTO. Rendered with MapLibre. FCC BDC mobile coverage processed by Carrierlytics.

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Cell phone coverage rankings by network in Diamond Bar, CA

#1

T-Mobile

Coverage Score 97.0
In Diamond Bar, CA
Overall
100.0%
4G LTE
100.0% avg. -86 dBm 4G LTE signal where 4G LTE coverage exists: avg. -86 dBm
5G
99.4% avg. -82 dBm 5G signal where 5G coverage exists: avg. -82 dBm
Fast 5G
93.8% avg. -81 dBm Fast 5G signal where Fast 5G coverage exists: avg. -81 dBm
Los Angeles County, CA covered 78.2%
#2

Verizon

Coverage Score 90.0
In Diamond Bar, CA
Overall
98.1%
4G LTE
98.1% avg. -87 dBm 4G LTE signal where 4G LTE coverage exists: avg. -87 dBm
5G
95.4% avg. -94 dBm 5G signal where 5G coverage exists: avg. -94 dBm
Fast 5G
85.5% avg. -92 dBm Fast 5G signal where Fast 5G coverage exists: avg. -92 dBm
Los Angeles County, CA covered 80.6%
#3

AT&T

Coverage Score 85.8
In Diamond Bar, CA
Overall
99.7%
4G LTE
99.7% avg. -97 dBm 4G LTE signal where 4G LTE coverage exists: avg. -97 dBm
5G
98.5% avg. -102 dBm 5G signal where 5G coverage exists: avg. -102 dBm
Fast 5G
94.4% avg. -102 dBm Fast 5G signal where Fast 5G coverage exists: avg. -102 dBm
Los Angeles County, CA covered 77.5%

County coverage is shown for surrounding-area context and uses land-area only coverage.

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Best phone plans for Diamond Bar, CA

Best phone plans on T-Mobile's network for Diamond Bar, CA

97.0 T-Mobile coverage score Ranked #1 in Diamond Bar, CA
Best family plan
79.5 Value Score

T-Mobile Better Value

Fair Value

Price
$140.01/mo for 3 lines ($46.67/line)
Data
Unlimited
Hotspot
Unlimited
View plan
See all plans on T-Mobile Compare all phone plans

Coverage by ZIP code in Diamond Bar, CA

ZIP code areas can extend beyond city limits, so this table is best used for local comparison around the city.

ZIP Code AT&T T-Mobile Verizon
91765 92.9% 92.9% 84.9% 82.2% 96.6% 96.6% 91.2% 81.5% 88.1% 87.1% 80.8% 64.7%
91789 99.7% 99.7% 98.0% 87.8% 100.0% 100.0% 99.7% 97.1% 99.1% 99.1% 98.8% 97.4%

About The Coverage Data

Coverage and signal estimates are derived by Carrierlytics from carrier-reported data in the FCC’s National Broadband Coverage Map, last updated in June 2025. “Percent covered” shows how much of the city or ZIP code area has a carrier signal, whether weak or strong. Signal bars show the estimated average signal strength in areas of Diamond Bar, CA where that carrier has coverage.

If a carrier says you should have service but you do not, run a challenge test with the FCC Mobile Speed Test App. The FCC uses those results to check carrier-submitted coverage data and requires a carrier response when enough tests show a pattern of inaccurate coverage reporting.