Telecom Engineering Tool

SMS Segment & Character Calculator

Calculate exact carrier segment boundaries, detect UCS-2 unicode switches, and prevent accidental bill shock from concatenated multipart messages in real time.

Live Payload Inspector

Detected Encoding

GSM-7

7-bit (160 chars/seg)

Billable Segments

Carrier billable units

Total Characters

Raw character count

Remaining in Seg

160

Before next split

Est. Cost (USD)

$0.0000

Baseline $0.0079 / unit

Standard Encoding GSM 03.38

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) signaling packet.

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

Multipart Packet UDH Overhead

Why Concatenated Messages Reduce Segment 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 carries 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).