Live count, segment splits, and per-send cost estimator.
Your message
For total cost projection
Default: Twilio US base rate
Results
Segments—
Characters
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Encoding
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Per Segment Limit
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Send cost
Cost per Recipient
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Total Send Cost
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Cost / Char Sent
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Optimization opportunities
About this calculator
SMS marketing economics live or die by segment count. A two-segment message costs twice what a one-segment message costs. A two-segment send to 100,000 subscribers costs 2× a one-segment send to the same list. At Klaviyo and Attentive scale this is real money — the difference between a 158-character message and a 162-character message can be five figures per send.
The encoding question is where most operators get tripped up. The GSM-7 alphabet is the default SMS encoding and fits 160 characters per segment. The moment you add a single character outside GSM-7 — most emojis, curly quotes from copy-pasting from a doc, em dashes, accented characters — the entire message switches to UCS-2 (Unicode), which fits only 70 characters per segment. A perfectly composed 155-character message with one rocket emoji becomes a 3-segment Unicode send, tripling cost.
The other gotcha is multi-segment overhead. Once a message spans more than one segment, each segment loses 7 characters to a User Data Header for client-side reassembly. So multi-segment GSM-7 fits 153 characters per segment, not 160; multi-segment Unicode fits 67 per segment, not 70. A 161-character GSM-7 message is 2 segments × 153 = 306 capacity, not 320.
Beyond cost, segment count affects deliverability and read rates. Single-segment messages deliver instantly. Multi-segment messages occasionally arrive out of order on older devices, and very long sends (4+ segments) sometimes get flagged as spam by carriers. Best practice for marketing SMS is to stay under 160 GSM-7 characters whenever possible — use a branded link shortener, drop unnecessary emojis, and consider whether the message could be MMS instead if visual content matters.
Frequently asked questions
Why does adding an emoji jump my segment count?
Standard SMS uses GSM-7 encoding which fits 160 characters per segment. Most emojis and many special characters force the message into UCS-2 (Unicode), which only fits 70 characters per segment. A 50-character message with one emoji becomes a 1-segment Unicode message; a 100-character message with one emoji becomes a 2-segment message and costs double.
What characters break GSM-7 encoding?
Most emojis, smart quotes (curly " " ʼ), em/en dashes (— –), the ellipsis (…), accented characters from many languages (â, ñ, ç), and some currency symbols. The GSM-7 alphabet covers basic Latin letters, digits, common punctuation, and a small set of symbols. If your message contains anything outside that set, the entire message switches to Unicode encoding.
How are multi-segment messages counted?
When a message exceeds one segment, each segment loses 7 characters to a User Data Header (UDH) used for reassembly. So GSM-7 multi-segment messages allow 153 characters per segment instead of 160; Unicode multi-segment messages allow 67 characters per segment instead of 70. A 161-character GSM-7 message is 2 segments at 153 chars each = 306 capacity used.
What is a typical SMS cost per segment?
In the US, Twilio charges roughly $0.0079 per outbound segment (2026). Other providers (Postscript, Attentive, Klaviyo SMS) bundle segments into monthly plans that average $0.01-0.015 per segment after platform markup. Carrier fees add another $0.003-0.005 per segment depending on carrier. International rates vary dramatically — UK is similar, Brazil is higher, India is lower.
How can I reduce SMS costs?
Three big levers: keep messages under 160 characters when possible (single segment), avoid unnecessary emojis (Unicode forces 70-char segments), and use URL shorteners that produce short branded links rather than long marketing URLs. A typical promo SMS with one emoji and a long marketing URL is often 3-4 segments; tightening to 160 characters of GSM-7 cuts cost by 70-75%.