calc.engineer / LoRa & Meshtastic / LoRa Airtime

LoRa Airtime v1.0.0

Calculates LoRa packet time-on-air using the Semtech AN1200.13 formula. Computes symbol duration, preamble time, payload symbol count, effective data rate, and the minimum transmission interval for 1% duty cycle compliance. Essential for capacity planning in LoRaWAN and Meshtastic mesh networks. Accepts spreading factor (SF7-SF12), bandwidth (125/250/500 kHz), coding rate (4/5-4/8), payload size, header mode, CRC, and optional low data rate optimization. Feeds airtime_ms to channel_utilization for mesh load analysis.

feeds channel_utilization →
LoRa spreading factor (7-12). Higher SF = longer range but slower data rate.
LoRa channel bandwidth in kHz. Common values: 125, 250, or 500.
LoRa coding rate denominator (5-8). Represents 4/5 through 4/8 FEC ratio.
Application payload size in bytes (0-255).
Number of preamble symbols. LoRaWAN uses 8; raw LoRa may vary.
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/lora_airtime \
  -H "Content-Type: application/json" \
  -d '{"sf": …, "bw_khz": …, "cr": …}'

MCP: connect to https://calc.engineer/mcp and call lora_airtime.

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