A message and an SMS segment are different things
The message is what your customer reads. A segment is the unit used to carry that text across a mobile network. A longer message can arrive as one joined conversation while using more than one segment.
The SMS gateway counts those segments before a send. Each recipient uses one credit for each segment, so two segments sent to 100 valid recipients use 200 credits. Looking at the segment count is a useful habit even when the wording seems short.
Start with the encoding
A GSM-7 message can fit 160 units in a single segment. Once it becomes a multipart message, each segment holds 153 units because joining the parts needs space.
Sinhala, Tamil and other characters outside the GSM-7 alphabet switch the message to Unicode. The limits then become 70 UTF-16 units for one segment and 67 units per segment for a multipart message.
Some characters count differently from what you see on screen. GSM-7 extension characters, such as braces and the euro sign, use two units. Some emoji use two UTF-16 units. The live composer handles those details so you do not have to count them by eye.
A small edit can change the whole message
Adding a name, reference number or emoji can move a message into another segment. The effect is multiplied by the number of recipients, which is why reviewing the final version matters more than reviewing an early draft.
Keep essential information clear. Shortening a message is useful when it removes repetition, but removing the context your customer needs can make the message less helpful. Use the preview to make that tradeoff with the actual count in front of you.
- Review the exact final text, including any greeting or order reference.
- Check the encoding and segment count in the composer.
- For an API integration, call the estimate endpoint with the same message you plan to send.
- Multiply segments by valid recipients to understand the credits required, then check the bulk SMS rates.
Preview first, then send
The playground on the SMS gateway Sri Lanka homepage is a quick way to explore text length. The signed-in composer also considers the recipient list and your account balance. If you send through the API, POST /api/v3/sms/estimate returns the analysis without sending a message.
Use that feedback before a large bulk SMS campaign. It turns encoding from an unexpected charge into something you can see and adjust while you write.
