IoT Data Usage Calculator
Estimate cellular or LPWAN data per day, month, and year from payload size, overhead, message rate, and device count.
Estimating IoT data
A device's data bill is driven as much by overhead as payload: each message carries protocol headers, and for chatty transports the handshake can dwarf a few bytes of sensor data. This calculator totals both across your message rate and fleet size.
per message = payload + overhead
fleet / month ≈ per message × messages/day × devices × 30.44
Cutting message frequency, batching readings, or using a leaner transport (CoAP/UDP or a raw LPWAN frame instead of TCP+TLS) are the usual levers. Data here uses decimal units (1 kB = 1000 B), as mobile plans do.
Why overhead dominates small messages
Sensor payloads are often tiny — a temperature reading might be two or three bytes — but the message wrapping around them usually isn't. A TCP+TLS exchange can spend hundreds of bytes on handshake and headers before a single byte of data moves, so for infrequent small readings the overhead, not the payload, sets your bill. On metered cellular or LPWAN plans that difference decides whether a fleet fits its data budget.
Worked example
Say each reading is 10 bytes of payload plus 40 bytes of overhead: 50 bytes per message. At one message a minute that's 1440 messages a day, so per device that's about 72 kB/day, or roughly 2.2 MB/month. Across a 500-device fleet that's over 1 GB a month — and more than three-quarters of it is overhead. Batching six readings into one message would cut the message count sixfold and the total nearly as much.
The levers
Cutting message frequency, batching readings, and using a leaner transport (CoAP/UDP or a raw LPWAN frame instead of TCP+TLS) are the usual ways to bring data down. Data here uses decimal units (1 kB = 1000 B), as mobile plans do. Pair this with thebattery life calculator to trade off how often a device reports against how long it runs.
Overhead and retransmissions are the hidden cost
The payload is only part of what crosses the network. Protocol headers, handshakes, keep-alives and acknowledgements all add bytes, and on small payloads the overhead can exceed the data several times over — a 12-byte sensor reading inside a TLS session is not a 12-byte transmission. Cellular plans also bill in rounded increments per session rather than per byte. And any figure here assumes every message arrives first time; in a marginalradio link, retransmissions can multiply real usage.