📡Wireless
LoRa Airtime Calculator
Calculate LoRa/LoRaWAN airtime, packet duration, and symbol count based on spreading factor, bandwidth, coding rate, and payload size.
Results
Symbol Time
32.77 ms
Payload Symbols
28
Total Symbols
40.25
Airtime
1.319 s
Formula Explanation
The symbol time for LoRa modulation is calculated as:
Tsym = 2SF / BW
Where SF is the Spreading Factor (7–12) and BW is the Bandwidth in Hz.
The total airtime is the sum of the preamble symbols (12.25 symbols) plus the payload symbols, multiplied by the symbol time:
Tair = (Npreamble + Npayload) × Tsym
The payload symbol count depends on the Spreading Factor, Coding Rate, payload size, header mode, and low data rate optimization (explicitly enabled for SF ≥ 11).
Reference: Airtime by SF (BW = 125 kHz, CR = 4/5, payload = 20 bytes)
| SF | Tsym | Payload Symbols | Airtime |
|---|---|---|---|
| SF7 | 1.02 ms | 43 | 56.6 ms |
| SF8 | 2.05 ms | 38 | 102.9 ms |
| SF9 | 4.10 ms | 33 | 185.3 ms |
| SF10 | 8.19 ms | 33 | 370.7 ms |
| SF11 | 16.38 ms | 33 | 741.4 ms |
| SF12 | 32.77 ms | 28 | 1.319 s |