Rules note: You need an FCC license to transmit on GMRS (47 CFR 95.1705). Use only FCC-certified GMRS radios, and stay within the power and channel limits for your station type. This is general information, not legal advice. The eCFR text of Part 95 Subpart E is the authority.
Ask how far GMRS reaches and you’ll hear everything from “a mile” to “fifty miles.” The FCC’s own answer is a range: “A GMRS user can expect a communications range of one to twenty-five miles depending on station class, terrain, and repeater use” (FCC). This guide explains why the range varies so much, and how to estimate yours.
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Why line of sight rules on UHF
GMRS uses frequencies around 462 and 467 MHz (95.1763). Midland’s FAQ explains that these frequencies “primarily depend on line of sight for optimal range,” unlike CB, which can sometimes travel farther via the ionosphere (Midland). In practice, anything solid between the two antennas costs you range: hills, ridges, dense trees and buildings.
The radio horizon formula
Over smooth ground, the farthest an antenna can “see” is its radio horizon. A common approximation is:
Radio horizon (miles) ≈ √(2 × antenna height in feet)
This comes from geometry on a sphere using an “effective Earth radius” 4/3 the real radius, which accounts for the way the normal atmosphere bends radio waves slightly. The derivation: √(2 × 4/3 × 3,959 mi × h ÷ 5,280) ≈ √(2h).
Two stations can talk on a clear path if the sum of their horizons is greater than the distance between them.
Worked examples
| Station A | Station B | Horizon A | Horizon B | Clear-path limit |
|---|---|---|---|---|
| Handheld at 6 ft | Handheld at 6 ft | 3.5 mi | 3.5 mi | ≈ 6.9 mi |
| Vehicle antenna at 7 ft | Handheld at 6 ft | 3.7 mi | 3.5 mi | ≈ 7.2 mi |
| Base antenna at 30 ft | Vehicle at 7 ft | 7.7 mi | 3.7 mi | ≈ 11.5 mi |
| Repeater antenna at 200 ft (hill or tower) | Handheld at 6 ft | 20.0 mi | 3.5 mi | ≈ 23.5 mi |
Arithmetic: √12 = 3.46, √14 = 3.74, √60 = 7.75, √400 = 20.0.
These are best cases over flat, open ground. The repeater line lands near the top of the FCC’s “one to twenty-five miles.” Real paths through hills and trees are usually shorter. Check your own numbers with the range estimator, which also lets you apply a terrain allowance.
What power does and doesn’t do
Power within the legal limits (95.1767) improves the signal at the far end. That can turn a scratchy contact into a clear one. Power doesn’t extend the horizon. A 50 W radio with a low antenna behind a ridge will still lose to a 5 W handheld standing on the ridge.
Repeaters: borrowing height
A repeater’s antenna sits high on a hill or tower, so its horizon is much larger. Your handheld only needs to reach the repeater, and the repeater retransmits on the 462 MHz output (95.1763). This is why the FCC lists “repeater use” as a range factor. See GMRS repeaters explained.
Other factors
- Coax cable loss: longer and thinner cables lose more signal at UHF. Keep runs short and use the cable your antenna maker recommends.
- Antenna gain and pattern: see antenna height and gain. On channels 1–7 the limit is ERP, so gain counts toward it (95.1767(b)).
- Body and vehicle blocking: a handheld inside a car loses signal through the metal body. An external antenna fixes this.
- Interference and busy channels: channels are shared (95.359).
Planning a family network
- List your stations and heights: handhelds at about 6 ft, vehicles at roof height, a base antenna on the house.
- Run each pair through the range estimator and note the clear-path limits.
- Look at a map for ridges and dense woods between points. Cut your plan to half the clear-path number or less where the path is obstructed.
- Fill gaps with a higher base antenna, a relay point on high ground, or a repeater whose owner allows your use (95.1705(d)).
- Test with short, identified transmissions (95.1731(b)(3)) and adjust.
Reading range claims on packaging
Radio boxes often print a single large mileage number. Midland’s own spec sheets qualify these figures: maximum range assumes open water or rural areas under optimum conditions. Read that number as a best case between elevated points, not a figure for a typical neighborhood. To compare radios fairly, look at where the antenna will sit and what the rules allow for that station type. A 50 W mobile with a roof antenna and a 5 W handheld on your belt are different tools, whatever the box says. The estimator above, plus a realistic terrain allowance, gives a better planning number than any packaging claim.
FAQ
Why do boxes claim 36 miles?
Marketing figures assume ideal conditions. Midland’s spec sheets say maximum range “can only be achieved over water or open rural areas under optimum conditions.”
How do I get more range legally?
Raise the antenna, use a mobile or base with an external antenna, cut coax losses, or use a repeater.