How SMS segments work for SMS alerts

STOQ’s SMS charges are based on segments, the individual text units carriers transmit and bill separately. You’re charged per segment, not per message, so a message that splits into two segments costs twice as much as a one-segment message. Understanding segments helps you write concise templates and keep your SMS costs predictable.

Why segments matter

• Control costs. You’re charged per segment. A 2-segment SMS costs twice a 1-segment one.
• Write effective templates. Character limits push you to keep the key information tight.
• Predict spending. Knowing your average segments per message lets you estimate the monthly cost.
• Improve reliability. Very long, multi-segment messages can occasionally arrive out of order.

What is a segment

A segment is a billable unit of text. How many characters fit in a segment depends on the encoding, and the encoding depends on which characters you use.

GSM-7 (standard characters)

Used for letters, numbers, spaces, and common punctuation:

Segments	Capacity
1 segment	up to 160 characters
2 segments	up to 306 characters (153 per segment)
3 segments	up to 459 characters

Multi-segment messages reserve about 7 characters per segment to stitch the parts together.

UCS-2 (special characters)

Triggered by emojis, accented letters, non-Latin scripts, or special symbols:

Segments	Capacity
1 segment	up to 70 characters
2 segments	up to 134 characters (67 per segment)
3 segments	up to 201 characters

Even a single special character switches the whole message to UCS-2, which sharply cuts the capacity.

Quick reference

Encoding	1 segment	Each extra segment
GSM-7	160 chars	153 chars
UCS-2	70 chars	67 chars

How STOQ counts characters

While you edit an SMS, the content editor shows a Total characters counter and the resulting segment count. It recommends keeping messages short because two things add length beyond what you type:

• Unsubscribe text is appended to every SMS automatically (required for compliance) and counts toward the total.
• Variables expand. A placeholder like {{product.title_incl_variant}} becomes the actual product name when sent, which is usually longer than the variable itself.

So a template that looks like 120 characters in the editor can send as 170+ characters and split into two segments.

Examples

• Short (1 segment): “Hi! {{product.title}} is back in stock. Grab yours: {{product.purchase_link}}” renders to roughly 135 characters and stays 1 GSM-7 segment.
• Longer (2 segments): “Great news! {{product.title_incl_variant}} is back at {{shop.name}}. Limited stock, order now: {{product.purchase_link}}” renders to about 210 characters and becomes 2 segments.
• Emoji (2 segments): “🎉 {{product.title}} is back! Shop now: {{product.purchase_link}}” is short, but the emoji forces UCS-2, so the 70-character single-segment limit is exceeded and it becomes 2 segments.

At $0.025 per segment (US and Canada), 500 alerts a month costs $12.50 as 1-segment messages, but $25.00 if each splits into 2 segments.

Tips to keep the segment count low

• Keep the editor’s Total characters under about 140.
• Avoid emojis and special symbols (they switch you to UCS-2).
• Use {{product.title}} instead of {{product.title_incl_variant}} where you can.
• Preview with a sample product name to see the rendered length before you rely on it.
• Cut unnecessary words, and use a short or branded purchase link.

Where to view segment usage

1. Open your usage

   1. In the left menu of the STOQ app, click Plans.
   2. On the Usage card, click the Back in stock alerts count.
   3. In the breakdown, review the SMS totals and segments sent this month.

Troubleshooting

Charges are higher than expected

Your messages are probably splitting into multiple segments. Check the Total characters count in the editor and shorten the message.

It says 2 segments even though I'm under 160 characters

Variables expand when sent, so the rendered message is longer than the template. Use the editor’s preview with a sample product name to see the real length.

2 segments with no emoji

A hidden special character (a curly quote, a long dash, or an accented letter) forces UCS-2, which drops the limit to 70 characters. Replace it with a standard character.

FAQ

How are segments charged?

Each segment is charged at the per-segment rate for the destination country, so a 2-segment message costs twice a 1-segment one. See SMS alert pricing and charges.

Do emojis really change the cost?

Yes. A single emoji switches the message to UCS-2, cutting the single-segment limit from 160 characters to 70, which usually adds a segment.

Does the unsubscribe text count?

Yes. The mandatory unsubscribe text is appended to every SMS and counts toward the total characters.

Can I see the exact segment count before sending?

The editor’s character counter and preview are your best guide. The carrier sets the final segment count at delivery, and per-message breakdowns aren’t shown in the app.

Related guides

SMS alert pricing and chargesPer-segment prices by country and how billing works.

Set up SMS alertsTurn on SMS, verification, and cost.

Check your plan usage and remaining alertsSee alerts and segments sent this month.