# How much data does my device need?

> A practical way to estimate monthly data for a connected device, with worked figures for common devices and the plan each one fits.

Choosing a SIM · 20 November 2025

Most connected devices use very little data, and the few that use a lot use it for one reason: video. Getting the plan right means estimating what your device actually sends, then leaving sensible headroom. This guide shows how.

## The calculation

Monthly data is simply how much a device sends each time, multiplied by how often it sends, plus anything large it does now and then:

**monthly data = (size of each message × messages per day × 30) + occasional large transfers**

Three things are easy to forget:

- **Overhead.** Every message carries protocol overhead on top of its contents. A 100-byte reading can cost several hundred bytes on the network, so round small messages up generously.
- **Keepalives.** Many devices check in regularly even with nothing to report. A check-in every minute adds up over a month.
- **Firmware updates.** A single update can be larger than months of normal traffic. Allow for one or two a year.

## Typical figures

These are estimates with the assumptions stated, to show the scale. Your device's manual or a week of real usage in the portal will always beat a table.

| Device | Typical pattern | Rough monthly use | Plan that fits |
|---|---|---|---|
| Card machine | A few kilobytes per transaction | Well under 50 MB | 50 MB |
| Alarm communicator | Small regular check-ins, rare alarms | Under 50 MB | 50 MB |
| Meter or data logger | A reading every 15 to 60 minutes | A few MB | 50 MB |
| GPS tracker | A position every minute while moving | 5 to 20 MB | 50 MB |
| Vending telemetry | Periodic stock and sales reports | Under 50 MB | 50 MB |
| EV charger | Session data, status, occasional firmware | 50 to 250 MB | 250 MB |
| Trail camera, photos only | A few photos a day | 100 MB to 1 GB | 1 GB |
| CCTV, motion clips only | Short clips on events | 1 to 5 GB | 5 GB |
| Router as broadband backup | Depends what fails over | 1 to 5 GB or more | 5 GB |
| Digital signage | Content updates, not streaming | 1 to 5 GB | 5 GB |

## A worked example

A tracker sends a position every 60 seconds while the vehicle moves, and the vehicle moves eight hours a day. Allow 500 bytes per report once overhead is included.

- 60 reports an hour × 8 hours = 480 reports a day
- 480 × 500 bytes = about 240 KB a day
- × 30 days = about 7 MB a month, plus a little for check-ins and the odd update

That fits easily in 50 MB, at £0.90 a month on UK 4-network. The same arithmetic for a camera uploading video gives an answer a thousand times larger, which is why [CCTV gets its own guide](/cctv-camera-data-usage).

## Leave headroom, then check

Pick the plan your estimate fits with room to spare, then watch the first few weeks of usage in the portal. If the device runs out, the SIM pauses rather than charging overage, and you can move it to a larger plan straight away, paying only the difference for the rest of the month. Usage alerts in the portal, and the 80% and 100% webhooks for those using the API, warn you before that happens.

## Common questions

### What if I choose too small a plan?

The SIM pauses when it reaches its allowance instead of charging overage. Move it to a larger plan in the portal and it carries on straight away; you pay only the difference for the rest of the month.

### Can I change a SIM's plan later?

Yes, in the portal or through the API. An upgrade takes effect straight away; a downgrade takes effect at renewal.

### Which plans are available?

UK plans of 50 MB, 250 MB, 1 GB and 5 GB a month, on UK 4-network or the cheaper UK 3-network. 1 GB on UK 4-network is £2.40 a month.

## Recommended plan

250 MB, UK 4-network: £1.20 a month per active SIM, ex VAT.

Source: https://thingsim.com/how-much-data-does-my-device-need