IoT & LPWAN Calculators
2 free calculators with formulas and worked examples.
LoRa and Bluetooth Low Energy link budgets: receiver sensitivity from the radio's own formulas, LoRa time on air and duty-cycle off-time, path loss in free space, Okumura–Hata or ITU-R P.1238 indoor models, link margin and range.
LoRa Link Budget
LoRa link budget from the Semtech SX1276 formulas: receiver sensitivity by spreading factor and bandwidth, symbol time, time on air with automatic low-data-rate optimisation, duty-cycle off-time, free-space or Okumura–Hata path loss, link margin and maximum range.
BLE Link Budget
Bluetooth Low Energy link budget by PHY: data rate and Core Specification receiver sensitivity for LE 1M, LE 2M and LE Coded, path loss in free space or the ITU-R P.1238 indoor model, received power, link margin and maximum range.
About IoT & LPWAN Calculators
Low-power wireless links are budgeted like any other radio link — transmit power, antenna gains, path loss and receiver sensitivity — but IoT radios trade data rate for sensitivity far more aggressively than cellular or Wi-Fi, and in most licence-exempt bands regulation also limits how often a device may transmit.
LoRa spreads each symbol over 2^SF chips. Every step of spreading factor doubles the symbol time and lowers the SNR the demodulator needs by 2.5 dB: the Semtech SX1276 datasheet gives −7.5 dB at SF7 and −20 dB at SF12, so a 125 kHz receiver with a 6 dB noise figure reaches about −124.5 dBm at SF7 and −137 dBm at SF12. The price is airtime. A 51-byte packet takes 102.7 ms at SF7 and 2.47 s at SF12, where low-data-rate optimisation is mandatory, and under the 1% duty cycle of the EU 868.0–868.6 MHz sub-band every transmission must be followed by 99 times its airtime of silence. Okumura–Hata gives the median path loss to a gateway mast between 1 and 20 km.
Bluetooth Low Energy has four physical layers. LE 1M and LE 2M carry 1 and 2 Mb/s and must meet a −70 dBm reference sensitivity; the coded PHY repeats each bit to reach 500 kb/s at −75 dBm (S=2) and 125 kb/s at −82 dBm (S=8), the long-range mode. Those are the worst a compliant receiver may have, and most radios beat them by 20 dB or more, so a datasheet value gives a truer range. Indoors, ITU-R P.1238 replaces free space with measured site-general coefficients: through an office at 2.44 GHz and 10 m the median loss is 63.3 dB, against 60.2 dB in free space, and it grows with distance as 23.9 dB per decade instead of 20.