LoRa Antenna Length Calculator
Quarter-wave wire lengths for every LoRa region — 7.8 cm at 915 MHz, 8.2 cm at 868, 8.3 cm for India's 865 — and why a wrong-band antenna wrecks the link budget.
Preset: quarter wave at US915 → ~7.8 cm. Set f = 868 for Europe (8.2 cm), 866 for India (8.3 cm), 433.92 for LoRa-433 (16.4 cm). The ground plane (PCB or counterpoise wire) is the other half of the antenna.
LoRa Antenna Length Calculator computes quarter-wave antenna lengths for every LoRa regional band — 915, 868, 865 (India) and 433 MHz — free, instant and private in your browser. LoRa/LoRaWAN, Meshtastic and Helium builders matching antennas to their regional band use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About LoRa Antenna Length Calculator
LoRa Antenna Length Calculator computes quarter-wave antenna lengths for every LoRa regional band — 915, 868, 865 (India) and 433 MHz using the standard engineering relation: L = 0.25·(c/f)·k → 7.8 cm at 915 MHz, 8.2 cm at 868, 8.3 cm at IN865, 16.4 cm at 433.92. Worked live: a US915 node wants a 7.8 cm radiator; screwing on a 433 MHz antenna instead costs double-digit dB — kilometres of range. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use LoRa Antenna Length Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use LoRa Antenna Length Calculator?
- ✓Implements the real formula — L = 0.25·(c/f)·k → 7.8 cm at 915 MHz, 8.2 cm at 868, 8.3 cm at IN865, 16.4 cm at 433.92 — with the substitution shown, not a black box
- ✓Built for LoRa/LoRaWAN, Meshtastic and Helium builders matching antennas to their regional band
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate lora antenna length?+
Quarter-wave antenna lengths for every LoRa regional band — 915, 868, 865 (India) and 433 MHz follows L = 0.25·(c/f)·k → 7.8 cm at 915 MHz, 8.2 cm at 868, 8.3 cm at IN865, 16.4 cm at 433.92. For example, a US915 node wants a 7.8 cm radiator; screwing on a 433 MHz antenna instead costs double-digit dB — kilometres of range. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Which LoRa band does India use?+
IN865: 865–867 MHz, per WPC licence-exempt rules. The quarter wave is 8.3 cm — an 868 MHz (EU) antenna is only 3 MHz off and works essentially perfectly, while a 915 MHz antenna is 5.5 % off resonance and measurably down. Check the firmware region setting AND the antenna band together.
Why must I never power a LoRa module without an antenna?+
With no load on the RF port, transmit power reflects back into the power amplifier. SX127x/SX126x modules at +20 dBm into an open SMA are a documented cause of dead radios — and a join request can fire the PA the moment firmware boots. Attach the antenna (any antenna) or a 50 Ω dummy load first, every time.
Is the LoRa Antenna Length Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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