IoT Formula Calculator

Calculate common IoT design values and see what each number means

animation
fundamentals
formulas
beginner
Animation Beginner formula lab Units and checks

IoT Formula Calculator

Use common IoT formulas without treating them as magic. Change the inputs, step through the calculation, and check whether the result is healthy, marginal, or unrealistic.

Link budget active formula family
-67.0 dBm headline result
Healthy margin plain-language check
What
A guided calculator for RF range, battery life, ADC resolution, sampling, and message overhead.
Why
IoT design decisions often fail because units, margins, or duty cycles are guessed instead of calculated.
Try First
Keep the default link budget and increase distance until the margin becomes marginal.
Notice
Small changes in units or duty cycle can produce large design changes.

Choose Formula

Wireless Inputs

Wireless Link Budget

Estimate received signal and margin after free-space path loss and extra real-world loss.

Healthy margin
Learning Support

Start with units

Most formula mistakes come from mixing units. Check whether distance is meters or kilometres, current is mA or uA, and frequency is Hz or MHz.

Look for margin

A result that only works in the ideal equation is risky. Wireless links need fade margin, and battery estimates need usable-capacity derating.

Use the diagnosis

The calculator explains whether the number is healthy, marginal, or likely to fail so you can connect arithmetic to design judgement.

Change one input

For learning, change one value at a time. That makes it easier to see which parameter controls the outcome.

Quick Reference

Free-space path loss

FSPL(dB) = 32.44 + 20log10(d_km) + 20log10(f_MHz)

At 1 km and 868 MHz, FSPL is about 90.0 dB before building, foliage, antenna, and fading losses.

Link budget

Rx = Ptx + Gtx + Grx - path loss - extra loss

Link margin is received power minus receiver sensitivity. More than 10 dB is a useful teaching target.

Battery life

life(h) = usable capacity(mAh) / average current(mA)

Average current must include active and sleep time. A short active burst can still dominate a sleepy device.

ADC step

LSB(V) = Vref / 2^bits

This teaching convention maps codes 0 to 2^N - 1. Noise can make the useful step larger than the ideal LSB.

Nyquist

sample rate >= 2 x highest signal frequency

Sampling near exactly 2x is fragile. Practical systems usually add a guard factor and anti-alias filtering.

Message overhead

efficiency = payload bytes / total message bytes

Small IoT messages can spend more bytes on headers than sensor data, especially with text protocols.

dBm to mW

mW = 10^(dBm / 10)

0 dBm is 1 mW, 10 dBm is 10 mW, and 20 dBm is 100 mW.

Current units

1 mA = 1000 uA

Sleep currents are often written in microamps. Convert before averaging with active current in milliamps.

Wireless Range CalculatorGo deeper on link budget and range planning. ADC Resolution VisualizerSee quantization and code steps visually. Power Budget CalculatorExplore more detailed power budgeting.