Meshtastic LoRa Range Calculator — 915 MHz Link Budget Estimator

Enter your TX power, antenna gains, Meshtastic modem preset, and terrain type to get a Friis link-budget estimate of your theoretical free-space range and a terrain-adjusted real-world estimate at 915 MHz — the North American Meshtastic band.

LoRa is remarkably long-range because its spread-spectrum modulation achieves receiver sensitivity down to −140 dBm — far below the thermal noise floor for narrowband radios. The Friis transmission equation quantifies how signal strength falls with distance in free space. Terrain — hills, buildings, trees, and even rain — is almost always the real limiting factor; the link budget tells you how much margin you have left after free-space loss before you run out of signal.

For a broader look at sovereign, decentralized mesh communications, see D-Central’s Meshtastic + LoRa mesh hub.

How the Friis link budget works

Radio signal strength falls with the square of distance (inverse-square law). The Friis equation captures this precisely for free space:

FSPL(dB) = 32.44 + 20·log₁₀(f_MHz) + 20·log₁₀(d_km)

At 915 MHz:  FSPL = 91.67 + 20·log₁₀(d_km)

Link budget: FSPL_budget = P_tx(dBm) + G_tx(dBi) + G_rx(dBi) − L_sys(dB) − Sensitivity_rx(dBm)

Max range:   d_km = 10 ^ ( (FSPL_budget − 91.67) / 20 )

Source: ITU-R Recommendation P.525-4 (free-space attenuation)
        Semtech SX1262 datasheet rev 2.1 (receiver sensitivity typical values)

Every 6 dB added to the link budget (higher TX power, better antenna gain, or a more sensitive preset) doubles the maximum free-space range. Every additional dB of antenna gain on either end contributes equally; this is why a modest 6 dBi directional antenna at one node can extend range as much as quadrupling TX power.

Modem preset reference — 915 MHz

Sensitivity values below are typical figures derived from the Semtech SX1262 datasheet at 25 °C. Actual device sensitivity varies by hardware revision, temperature, and manufacturing tolerances. Verify against your specific device datasheet.

Preset names and radio parameters per Meshtastic LoRa configuration documentation. Verify current firmware defaults at meshtastic.org — presets have changed across firmware versions. Sensitivity figures are typical values from the Semtech SX1262 datasheet and vary by hardware.

Why the theoretical range looks so large

LoRa at SF12 achieves sensitivity around −137 to −140 dBm. For reference, 20 dBm TX + two 5 dBi antennas + LONG_SLOW preset gives a link budget of roughly 167 dB — enough free-space range to reach the horizon thousands of kilometres away. The Friis equation is physically correct for vacuum or clear atmosphere, but two factors dominate terrestrial deployments:

• Earth’s curvature. The radio horizon for a node at height h (metres) above flat terrain is approximately 3.57 × √h km per node — roughly 3.6 km for a 1 m antenna, 11.3 km for a 10 m antenna. Two elevated nodes combine: d_horizon ≈ 3.57 × (√h₁ + √h₂). Beyond this, the direct path is blocked by the Earth itself.
• Terrain and obstacles. Hills, trees, buildings, and Fresnel zone obstruction absorb or scatter signal well before the Friis limit. A typical mesh node on a residential rooftop (≈ 5 m) links reliably to 5–20 km; a node on a hill or tower at 50 m can cover 50–150 km to similarly elevated peers.

Use the theoretical Friis output to determine whether your link budget has enough margin — if the theoretical range exceeds your target distance by a wide margin, your link will close despite real-world losses. If theoretical range barely exceeds your target, even modest terrain loss will break the link.

Terrain and environment guide

Environment	Terrain factor	Typical scenario	Notes
Elevated LoS	70%	Hilltop relay, rooftop > 10 m, tower	Residual losses from Fresnel zone, ground reflection, polarisation mismatch
Open flat	55%	Farm fields, open water, tarmac, prairie	Ground multipath and marginal Fresnel clearance reduce efficiency
Suburban	35%	Low residential, gentle hills, scattered trees	Partial NLoS; wood-frame house adds ≈ 10–15 dB loss
Urban	18%	City streets, mixed building heights	Reflections and diffraction dominate; nodes on rooftops improve this considerably
Dense/indoor	8%	Concrete building interiors, dense forest, underground	Concrete adds ≈ 20–30 dB; foliage ≈ 0.2–1.5 dB/m depending on density

Terrain factors are informed engineering estimates. Actual attenuation varies with specific site conditions. A certified RF survey and real-world RSSI measurements are the only reliable method for link planning at close-call margins.

Canadian regulatory note — ISED licence-exempt operation

In Canada, Meshtastic devices operating in the 902–928 MHz band (LoRa 915 MHz) fall under Innovation, Science and Economic Development Canada (ISED) Radio Standards Specification RSS-210 (Licence-Exempt Radio Apparatus, Annex 8 — 902–928 MHz ISM band). Operation under RSS-210 does not require a radio licence from ISED. Consult the current RSS-210 specification on the ISED website or an Industry Canada certified technician for the applicable transmitter power and antenna gain limits before deploying. D-Central does not publish specific EIRP ceilings here because regulatory parameters are subject to amendment and must be verified against the current official text.

In the United States, the equivalent regulation is FCC Part 15.247 (902–928 MHz spread-spectrum systems). Most commercial Meshtastic hardware sold in North America is pre-certified for both ISED and FCC limits; check your device’s regulatory markings.

Tips for maximising real-world Meshtastic range

• Elevate your node. Moving a node from ground level (1 m) to a 10 m rooftop triples the radio horizon and often improves real-world range by 5–10× in terrain-limited scenarios.
• Upgrade the antenna. Replacing a stock rubber-duck (~2 dBi) with a 5–6 dBi fiberglass vertical adds 3–4 dB to the link budget, roughly doubling free-space range. Directional antennas (Yagi) help for fixed point-to-point links.
• Minimise cable losses. Each metre of RG-58 at 915 MHz loses approximately 0.5–0.7 dB. Use LMR-400 or similar low-loss coax for outdoor antenna runs over 3 m, or mount the node directly at the antenna feed point.
• Choose the right modem preset. LONG_FAST is the community default and works for most mesh topologies. Switch to LONG_SLOW or VERY_LONG_SLOW only for fixed point-to-point links where throughput is not critical — but note that all nodes in a mesh must share the same channel/preset.
• Check the community map. The Meshtastic MQTT community map shows active nodes worldwide and is invaluable for planning node placement and coverage gaps.
• Use repeater nodes. Meshtastic is a mesh — each node extends the network. A well-placed solar-powered node on a hilltop serves as a relay for dozens of portable nodes below.

Frequently asked questions

Why is the theoretical Friis range sometimes thousands of kilometres?

The Friis transmission equation models pure free space with no obstructions and infinite signal propagation. LoRa at SF12/LONG_SLOW achieves such deep receiver sensitivity (around −137 dBm) that the free-space link budget mathematically closes at very large distances. In practice, Earth’s curvature limits terrestrial line-of-sight to tens of kilometres (depending on node height), and terrain absorbs most of that remaining margin. The Friis figure tells you how much budget headroom you have — a large theoretical range means your link can tolerate significant real-world loss and still close.

Which Meshtastic modem preset gives the longest range?

VERY_LONG_SLOW (SF12, BW=62.5 kHz) provides the best receiver sensitivity — approximately −140 dBm — and therefore the greatest link budget. However, it has a very low bit rate (≈ 61 bps) and long time-on-air, which can cause channel congestion in a busy mesh. LONG_FAST (the default) is a practical compromise: it achieves −131.5 dBm sensitivity with enough throughput for text messaging and position updates, and is compatible with the broader Meshtastic community. Use LONG_SLOW or VERY_LONG_SLOW for fixed long-haul links where all nodes run the same preset.

How much does antenna gain actually improve range?

In the Friis equation, range scales as 10^(G/20) per antenna gain increment in dBi. A 6 dBi antenna gain improvement at one end doubles the free-space range. Adding 6 dBi on both ends gives 4× range. In practical terms, replacing stock 2 dBi antennas with 6 dBi fiberglass verticals on both nodes adds 8 dBi total — roughly 2.5× theoretical range. Terrain-limited deployments see smaller gains, but antenna elevation often matters more than gain specification.

What does ISED RSS-210 mean for Meshtastic in Canada?

RSS-210 is Canada’s regulatory standard for licence-exempt radio apparatus. Meshtastic devices operating at 915 MHz in Canada fall under RSS-210’s 902–928 MHz ISM band provisions. No radio licence is required. Commercial Meshtastic hardware certified for North American markets carries both ISED and FCC certification marks (IC: XXXXXX and FCC ID: XXXXXX on the device label), confirming it meets applicable power and emission limits. Builders of custom Meshtastic hardware should verify compliance with the current RSS-210 standard directly on the ISED website before deploying.

My nodes are 5 km apart but can’t connect — is the link budget the problem?

At 5 km, the Friis FSPL at 915 MHz is approximately 91.67 + 20·log₁₀(5) = 105.6 dB. For LONG_FAST with 20 dBm TX and 2 dBi antennas each side, your budget is 20 + 2 + 2 − 0.5 − (−131.5) = 155 dB — leaving 155 − 105.6 = 49.4 dB of margin. That margin is ample; the link budget is almost certainly not the problem. More likely causes: line-of-sight obstruction (terrain, buildings), antenna orientation (vertical must be vertical), channel mismatch between nodes, or firmware/channel configuration issues. Check RSSI and SNR in the Meshtastic app — if RSSI is around −120 to −130 dBm or SNR is below −15 dB, you are at the sensitivity floor and a better antenna or higher node elevation is needed.

Does this calculator apply to 868 MHz (EU) Meshtastic?

This calculator is fixed at 915 MHz for the North American band plan (Canada and the United States). For EU nodes at 868 MHz, the Friis constant changes: FSPL_const = 32.44 + 20·log₁₀(868) = 91.20 dB — a difference of about 0.5 dB, which has negligible practical impact on range estimates. Modem preset parameters and regulatory limits (ETSI EN 300 220) differ for the EU band; consult the Meshtastic region configuration documentation.

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