SMS units
Your organisation's SMS wallet holds units. One unit pays for one SMS part. The API reports everything in units — it never shows prices.
You buy units in the app (SMS → Wallet). The price per unit depends on how many you buy; see pricing.
How many parts is my message?
| Message length | Parts (units per recipient) |
|---|---|
| Up to 160 characters | 1 |
| 161 – 306 characters | 2 |
| 307 – 459 characters | 3 |
| Longer | 1 part per 153 characters, rounded up |
Longer messages are split into 153-character parts because each part carries a few characters of joining information. The maximum message length is 1,600 characters.
:::caution Special characters Part counts assume the standard GSM character set (letters, numbers, common punctuation). Emoji and some special characters can make a network split a message into more, shorter parts. Keep messages to plain text where possible. :::
Units in API responses
| Field | Where | Meaning |
|---|---|---|
units_available | balance, send, batch receipt | Units left in the wallet |
sms_parts | send, status, batch | Parts (units) for that message |
units_used | send (up to 50 numbers) | Units used by this request |
units_required | batch receipt (51+ numbers) | Units the batch will use |
When are units used?
- Units are used when a message is handed to the network.
- Numbers that have opted out are skipped and use no units.
- Before sending, CloudMetis checks you have enough units for the whole request. If not, nothing is sent and you get
402 insufficient_units. - Sandbox (test key) messages never use units.