SMS Segment & Character Calculator

Calculate exact carrier segment boundaries, detect non-GSM unicode characters, and prevent accidental bill shock from multipart messages.

Detected Encoding

GSM-7

7-bit Standard (160 chars/part)

Billable Segments

Carrier billable units

Total Characters

Raw character length

Remaining in Segment

160

Until next segment triggers

Estimated Cost (USD)

$0.0000

At $0.0079/segment baseline

GSM-7 vs UCS-2 Encoding Mechanics

Standard SMS networks use GSM 03.38 7-bit default alphabet, which packs 160 characters into a single 140-byte (1,120-bit) payload.

The presence of even a single non-GSM character (such as Cyrillic, emoji, or unsupported punctuation) forces carriers to switch the entire message to UCS-2 16-bit encoding, dropping the single-message limit from 160 characters to 70 characters.

Why Concatenated Messages Reduce Limits

When an SMS exceeds the single segment threshold, carriers split the message into multipart packets. To allow recipient devices to reassemble the message correctly, each segment must carry a 6-byte User Data Header (UDH).

GSM-7 multipart: 153 characters per segment (7 characters reserved for UDH).
UCS-2 multipart: 67 characters per segment (3 characters / 6 bytes reserved for UDH).