Everyone "knows" a text message is limited to 160 characters — yet your phone happily sends a 400-character message without complaint. Both facts are true. The 160-character ceiling is real, but it applies to a single SMS segment. Cross it, and your message is silently split into pieces that get reassembled on the receiving phone — with the per-segment budget dropping to 153 characters. If you text friends, none of this matters. If you send appointment reminders, security codes, or marketing campaigns, the 160-vs-153 gap — and the 70-character trap hiding behind it — is what decides your bill.
The 160-character limit, and where it comes from
When SMS was designed in the 1980s as part of the GSM digital mobile standard, engineers had only a sliver of spare signaling bandwidth to work with — enough for messages of 1,120 bits. The standard's default alphabet, now called GSM-7, encodes each letter, digit, and common symbol in 7 bits. Do the division and you land on the famous number: 1,120 ÷ 7 = 160 characters. That figure, settled in 1985, has outlived pagers, flip phones, and a dozen generations of smartphones. The limit itself has never changed; what changed is that phones learned to hide it by chaining messages together behind the scenes.
Where 153 comes from
When your message exceeds 160 characters, it isn't sent as one long text. It's split into concatenated segments, and every segment reserves a small header — about 7 characters' worth of space — that tells the receiving phone "you are part 2 of 3, reassemble me with the others." That header leaves 153 usable characters per segment. So the real progression is 160, then 306, then 459: a 200-character message is billed as two messages, with the second one barely half full. There is no partial credit for a half-empty segment.
One more subtlety: even inside GSM-7, a handful of characters — the euro sign, square brackets, the tilde, the backslash — are sent as doubles and each count as two characters. They rarely matter in casual texts, but they can quietly nudge a carefully trimmed 160-character marketing message over the line.
How many characters you actually get
Here's the full budget table for both encodings. GSM-7 covers plain Latin letters, digits, and standard symbols. UCS-2 kicks in the moment the message contains anything GSM-7 can't express.
| Segments sent | GSM-7 (plain text) | UCS-2 (emoji or non-Latin script) |
|---|---|---|
| 1 | 160 | 70 |
| 2 | 306 | 134 |
| 3 | 459 | 201 |
| 4 | 612 | 268 |
| 5 | 765 | 335 |
Notice how steep the right-hand column is: five UCS-2 segments hold fewer characters than two GSM-7 ones. That asymmetry is why a character budget that feels generous can evaporate so fast.
Why one emoji can triple your message
The table's right-hand column is where budgets go to die. Emojis, curly "smart quotes," em dashes, and every non-Latin script — Arabic, Chinese, Cyrillic, Hindi — do not exist in GSM-7. A single such character anywhere in the message forces the entire message into UCS-2, a 16-bit encoding that fits only 70 characters in a single segment and 67 per segment after that. The arithmetic is brutal: a 160-character message that would have been one segment becomes 161 UCS-2 characters, which spans three segments — because you added one smiley. In bulk messaging, that emoji is the most expensive character you will ever type.
What this costs when you send in bulk
For person-to-person texting, segments are a curiosity. For bulk senders they are a line item. Carriers and SMS gateways bill per segment, so a two-segment promotion sent to 10,000 contacts is 20,000 billable messages — and the emoji version is 30,000. The same message, edited to fit a single GSM-7 segment, costs a third of that. Other channels have their own hard limits — Twitter/X posts cap at 280 characters, and email subject lines get truncated around 60 on phones — but SMS is the only major channel that silently splits your message and charges per piece.
How to keep a message to a single segment
Five habits that keep a text inside the first segment:
- Count everything. Spaces, punctuation, the sender name, and the legally required opt-out line ("Reply STOP to unsubscribe") all consume the same 160-character budget.
- Stay in GSM-7. Use plain hyphens and straight quotes, not the curly ones autocorrect inserts from word processors and design tools.
- Say it in words, not pictures. "Grin" costs 4 characters; one emoji can single-handedly re-encode a 160-character message into three segments.
- Shorten your links. A full URL can eat 40+ characters; a short link frees most of that back.
- Verify before you blast. Paste the final copy into the WordlyCount counter for an exact character count, then confirm the segment preview in your gateway.
The rule of thumb worth memorizing: 160 for one plain message, 153 for each additional part, 70 if there's an emoji — and when in doubt, count before you send.