What are segments?

Segments are the billing units of SMS. Carriers do not charge per message — they charge per segment, and a message longer than one segment's capacity is split and billed once per part. One send can therefore cost one segment or four, and the segments column is the one that tracks what SMS campaigns actually cost. It is always NULL for email, which has no equivalent.

Formula

segments = Σ billable message parts across a campaign's sends

Worked example

A 240-character SMS in plain text splits into two segments; 10,000 sends bill 20,000 segments. Rewriting it to 155 characters brings it to one segment — the campaign's carrier cost halves with no change in audience. Worse: a single emoji or curly quote can switch the whole message to a smaller-capacity encoding and double the segment count of an otherwise short text.

How Saldo Metrics computes it

fact_messaging_performance stores platform-reported segments per SMS campaign or flow-message row, alongside sends and the dual-stored send_cost (as-billed currency plus EUR at the ECB rate). v_messaging_performance serves it per row; the segments-to-sends ratio is your average parts per message, and send_cost_base divided by sends — the cost-per-message column next to it — is where segment bloat becomes visible in euros.

Why it matters

SMS unit economics are decided at the keyboard. Email's marginal cost is near zero; an SMS campaign's cost scales linearly with segments, and net margin per message swings on whether copy fits in one part. A segments-per-send ratio noticeably above 1.0 is usually the cheapest optimization available in the whole messaging channel.

Common mistakes

• Watching sends while carriers bill segments. A "10,000-message" campaign at 2.1 segments per send is a 21,000-unit bill.
• Ignoring encoding. One special character can silently reduce per-segment capacity for the entire message; most SMS platforms preview the segment count — check it before sending.
• Comparing SMS campaign costs without normalizing per segment. Two campaigns with equal sends can differ 2–3× in cost purely on copy length.

Where you see this in the app

Marketing → Messaging, as the segments column of the campaign table (SMS rows only).