IoT Calculators

Calculators for battery-powered and wireless devices

Designing an IoT device means balancing three things that pull against each other: how long it runs on a battery, how far its radio reaches, and how much data it sends. These calculators help you plan each one. Thebattery life calculator turns a device's sleep-and-wake cycle into a runtime estimate, thebattery capacity table helps you pick a cell, and the data usage calculator sizes your cellular or LPWAN traffic.

On the wireless side, thepath loss andlink budget calculators estimate whether a signal will actually reach the other end with margin to spare, and theLoRa / ISM frequency reference covers the sub-GHz bands and duty-cycle limits by region. Together they let you sanity-check a low-power wireless design on paper before committing to hardware.

Where battery-powered designs actually go wrong

Almost every disappointing battery life comes down to the same thing: the sleep current, not the active current. A device that wakes for two seconds every ten minutes spends over 99% of its life asleep, so a quiescent draw of 50 µA rather than 5 µA cuts the life by most of an order of magnitude — while the radio power everyone worries about barely moves the total.

The second trap is capacity. A cell's rated milliamp-hours are measured at a gentle discharge and a comfortable temperature. Pull a burst of radio current from a coin cell at 0 °C and the usable capacity is a fraction of the label, because the internal resistance collapses the terminal voltage below the cutoff long before the chemistry is spent.

Getting a link to work

Range questions split into two calculations that are easy to confuse. Free-space path loss tells you what the distance alone costs, and it depends on frequency as well as range — which is why the same hardware reaches further at 868 MHz than at 2.4 GHz. The link budget then adds transmit power and antenna gains and subtracts that loss, giving a received level you compare against the receiver's sensitivity. The difference is your margin, and anything under about 10 dB will not survive rain, a passing van, or a slightly misaligned antenna. Real deployments lose far more than free space predicts, so treat the result as a best case and design margin in deliberately.

Regional rules are not optional

ISM band limits differ by region in ways that change what you can build, not just what you must declare. EU 868 MHz imposes a duty cycle — commonly 1% — so a device cannot legally transmit whenever it likes. US 915 MHz instead limits dwell time per channel and expects frequency hopping. A design that is fine in one region may be unlawful in the other with no hardware change at all.