SMS Length, Segments & Cost

On SMS, length is cost. A message longer than a single SMS is split into multiple segments, and each segment is billed as a separate message. Because the per-message limit depends on the characters you use, the same-looking message can cost one SMS or three.

This guide is the practical companion to SMS Encoding & Message Length, which explains the underlying GSM-7 vs Unicode mechanics. Start there if the terms GSM-7, UCS-2, or concatenation are new.

Try it: SMS length calculator

Type or paste a message to see its encoding, character count, and how many billable segments it becomes. Toggle character detail to see exactly which characters are expensive.

Things worth trying:

• Paste a plain English message just over 160 characters — watch it become 2 segments of 153.
• Add a single emoji (😀) — watch the encoding flip to Unicode and the limit drop to 70.
• Replace a straight quote " with a curly quote " — same flip, no visible difference in the text.

How Sent counts segments

Sent computes the segment count from the message body using the standard GSM 03.38 rules — the same logic used for billing, so the count you see is the count you're charged for.

• GET /v3/messages/{id} returns a segments field: the total number of SMS parts the message split into. It's always 1 for non-SMS channels (WhatsApp, RCS) and for messages with no countable body.
• The dashboard shows the same segment count on each message in the activity view (e.g. "3 parts") for multi-part SMS.

How segments map to cost

Each SMS segment is billed as one message. The math follows directly from the encoding rules:

A 10-character message with one emoji and a 70-character all-text message both fit in one Unicode segment — but an 80-character message with an emoji is two. The emoji didn't add much length; it changed the limit.

Keep messages short and predictable

Practical guidance:

• Aim for a single segment. Under 160 GSM-7 characters (or 70 if the content is inherently Unicode) is the cheapest, most reliable outcome.
• Budget for variables. A template that's 150 characters with a short name can blow past 160 — into a second segment — when the name or a URL is long. Test with realistic, worst-case variable values, not "John."
• Budget for translation. A message comfortably within 160 GSM-7 characters in English will encode as Unicode (70-character segments) in Arabic, Chinese, Cyrillic, and most non-Latin scripts. The same content can be 1 segment in one language and 3 in another.
• Fewer parts, fewer failures. Beyond cost, each additional segment is another part that must arrive and be reassembled by the recipient's device and network. Long concatenated messages are marginally more prone to delivery issues than single ones.

Sandbox testing

Segment count is derived purely from the message body, so you can verify it without spending on real delivery: send with sandbox: true (see Testing & Debugging) and read the segments field back from the response. The count is identical to what a live send would bill.

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