What the numbers mean
- Link budget is how much signal loss the link can survive: transmit power plus both antenna gains, minus cable loss, minus the receiver's sensitivity. A bigger number means more range.
- Radio limit (path loss) is the distance at which the signal fades to the receiver's sensitivity, keeping a 10 dB safety margin for fading. The terrain choice changes how fast the signal fades with distance.
- Line-of-sight horizon is how far two antennas at the given heights can see each other over a curved earth. Radio waves bend a little, so the formula uses the standard 4/3 earth radius: horizon in km = 4.12 x (square root of height 1 in m + square root of height 2 in m).
- Realistic estimate is the smaller of the two. If the horizon is the limit, a higher antenna helps more than any upgrade. If the link budget is the limit, a better antenna or a slower preset helps.
- Fresnel zone radius is how wide the "tube" around the straight line between antennas must be. Keep at least 60% of it clear of hills, trees and roofs, or the signal drops sharply.
Three rules that matter more than the device
- Height beats power. Two handhelds at 1.5 m see each other for only about 10 km over flat ground. Put one on a hill or a mast at 30 m and the horizon grows to about 28 km.
- Each 6 dB doubles the distance in free space. A 3 dBi antenna instead of a 0 dBi stub on both ends adds 6 dB, about twice the range with clear sight.
- Slower presets hear further. LONG_SLOW is several dB more sensitive than LONG_FAST, but each message stays on air much longer. On a busy mesh that causes collisions. See presets explained.
Real-world records
Meshtastic users have reported links of more than 100 km between mountaintops and from balloons, because there the horizon is huge and nothing blocks the path. In a city between two handhelds at street level, a few hundred metres to 2 km is common. Both are normal: the calculator shows why. More examples with sources are in how far Meshtastic reaches.
Questions people ask
Is the calculator accurate?
It is an engineering estimate, not a measurement. It is good at telling you which limit you hit first and what to change. Real links can be shorter because of buildings, trees and interference, and longer from high places. The formulas and assumptions are listed on the methodology page.
What transmit power should I enter?
Use the legal maximum of your region, not the chip maximum. In Europe the EU_868 band used by Meshtastic allows up to 27 dBm (500 mW ERP); in the US 915 MHz band devices commonly transmit up to 30 dBm. Many boards top out at 22 dBm. Check frequencies by country.
Why does a higher-gain antenna sometimes give worse range?
High-gain omni antennas squash the signal into a flat disc. On a hill pointing down at a valley, or in a city with nodes above and below, a flat pattern can miss them. A 2 to 5 dBi antenna is the usual sweet spot. See the antenna guide.
Sources
Specs and prices were checked on the dates shown. Prices change often: check the shop before you buy.