LoRa calculator: airtime, duty cycle and range
LoRa reaches many kilometres with a few milliwatts – at the cost of data rate. The calculator shows how spreading factor, bandwidth and coding rate determine airtime per packet, permitted transmission rate and range.
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No installation, no sign-up needed.
What the page does
- Airtime per packet following the Semtech formula
- Duty cycle and possible packets per hour
- Sensitivity by spreading factor and bandwidth
- Link budget and range with Fresnel zone
- Comparison SF7 to SF12
- Presets for Meshtastic networks in Europe (EU_868)
Background
Each step of the spreading factor roughly doubles the airtime and gains about 2.5 dB sensitivity. In the 868 MHz band Europe limits transmission time, in many sub-bands to 1 % – 36 seconds per hour. The calculator shows how many packets of a given length that allows, and why a higher spreading factor is not always better.
In practice
How it works: choose spreading factor, bandwidth, coding rate and payload length. The calculator shows airtime and sensitivity and how often per hour you may transmit. Then enter transmit power, antenna gains and cable loss to estimate range. Short packets and the lowest workable spreading factor save both spectrum and battery.
Frequently asked questions
Do I need a licence for LoRa?
Not in the 868 MHz band, as long as power and airtime stay within the limits of the respective sub-band. In the amateur band the amateur rules apply.
How far does LoRa reach?
With line of sight and raised antennas many kilometres, indoors often only a few hundred metres. The calculator shows both cases.