SMS Segment Calculator
Count SMS segments online for free with real GSM-7 vs UCS-2 rules: 160/153 and 70/67 character limits, extension-character double counts, per-character
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What is SMS Segment Calculator?
The SMS Segment Calculator applies the real GSM 03.38 encoding rules to your message text. It detects whether the message fits GSM-7 (160/153 characters per segment) or must switch to UCS-2 (70/67), counts extension-table characters as two units, lists exactly which characters forced the switch, and estimates cost from your price per segment.
Key Benefits
- Know the true segment count before sending a campaign
- See exactly which characters break GSM-7 encoding
- Avoid surprise costs from one emoji or Thai character
- Estimate total cost with your own per-segment price
- Private and instant - everything runs in the browser
Common Use Cases
- •Planning SMS marketing campaigns within a budget
- •Checking OTP and notification templates for encoding traps
- •Estimating costs for multilingual messages with Thai or CJK text
- •Auditing gateway bills against expected segment counts
How to Calculate SMS Segments
- Type the message: Enter the exact SMS text you plan to send, including spaces and punctuation.
- Set your price: Enter your cost per segment from your SMS gateway or plan.
- Check encoding and segments: See whether the message is GSM-7 or UCS-2, the billable length, and segment count.
- Fix encoding traps: Review the listed characters that force UCS-2, then rewrite if you need the cheaper GSM-7 rate.
Key Features
- Full GSM 03.38 charset plus the extension table
- Automatic UCS-2 switching when any character is outside GSM-7
- 160/153 and 70/67 segment limits applied correctly
- Per-character warnings with Unicode codepoints
- Cost estimate from your price per segment
- Instant results - all math runs client-side
Frequently Asked Questions
Why does one Thai or emoji character change everything?
GSM-7 fits 160 characters per segment but only covers a Latin-centric set. Any character outside it switches the whole message to UCS-2, which holds just 70 characters per segment (67 when concatenated), often multiplying the segment count.
Why is the multi-segment limit 153 and not 160?
Concatenated messages reserve 7 bytes per segment for the segmentation header, leaving 153 single-byte characters for GSM-7 text (67 UCS-2 characters).
Which characters count as two units?
The ten GSM extension-table characters: caret, curly braces, square brackets, tilde, backslash, pipe and the euro sign. Each takes two length units and the tool flags them for you.
Does the tool guess the cost?
It estimates cost by multiplying the segment count by the price per segment you enter, using your gateway or plan pricing. It does not include taxes or per-message minimums some providers charge.