This tool runs entirely in your browser. The message you type is never sent, transmitted, or stored anywhere — not even to Interkey.
How SMS encoding works
SMS messages are sent using one of two character encodings. GSM-7 covers basic Latin letters, digits, and common punctuation, fitting up to 160 characters in a single segment. Unicode (UCS-2) is used whenever a message contains characters outside that set — including Arabic script — and fits only 70 characters per segment. A handful of "extended" GSM-7 characters (like { } [ ] ^ € ) count as two characters each even in GSM-7 mode.
Why segments matter
A message longer than one segment's limit is split into multiple parts for delivery and billed as multiple segments — invisibly stitched back together on the recipient's phone. A message that looks like "one text" can silently become two or three billed segments, especially in Arabic. See our SMS length and encoding guide for the full explanation.
Frequently asked questions
Does this tool store or send my message anywhere?
No. The calculation runs entirely in your browser using JavaScript — the text you type never leaves your device, is never transmitted to Interkey or any server, and is not logged by analytics.
Why does my message need 2 segments when it looks short?
If your message contains any character outside the GSM-7 set — including Arabic script, emoji, or certain symbols — the whole message switches to Unicode encoding, which fits only 70 characters per segment instead of 160.
What counts as a GSM-7 "extended" character?
A small set of characters (including { } [ ] ^ ~ \ | €) are part of the GSM-7 extension table and take up two character positions each, even though they display as one character.
Is this the same length limit for WhatsApp messages?
No — segment limits apply to SMS specifically. WhatsApp messages are not split into billed segments the same way; see our WhatsApp Business API page for that channel.