IoT data usage calculator
Estimate how much mobile data a device uses in a month, and what that means across a fleet. The figure counts what the mobile network meters: your payload, plus the protocol headers, security handshakes, keepalives and reconnects that travel with it.
How the estimate is built
The calculator counts bytes as a mobile network meters them: whole IP packets, in both directions. Units are decimal (1 MB is 1,000,000 bytes) and a month is 30 days, so every figure can be checked by hand.
- Each message is your payload plus the IP and TCP or UDP headers, the TLS or DTLS record overhead, the protocol's own header, any reply (an MQTT PUBACK, an HTTP response, a CoAP acknowledgement) and, over TCP, the acknowledgement packet.
- Each connection adds a DNS lookup, the TCP handshake and close, the security handshake and any protocol setup such as MQTT CONNECT. A device that opens a new connection for every message pays this every time, which is often the largest part of the bill.
- Keepalives are counted for MQTT when the gap between messages is longer than the keepalive interval.
- Firmware and file downloads are added in full for the month, not spread as a percentage.
- Tariff rounding, where a tariff rounds each data session up to a billing increment, adds half an increment per session on average.
Every overhead is an editable assumption with a stated default, not a typical figure for any device. Replace them with measurements from a representative device before sizing a tariff; the worked method is in How to estimate IoT data usage.
The calculator is open source: netavo-gds/iot-data-usage-calculator on GitHub.
Connect the fleet
Our multi-network IoT SIMs run on all four UK networks, with private access to your systems by IPsec, cloud interconnect, MPLS or L2TP.