Most people writing offer-heavy ecommerce texts treat MMS as the expensive option — the thing you use for a product photo when the campaign budget can afford it. That's mostly right, but there's a blind spot: a long SMS promo with an emoji or two doesn't stay a "single text." It quietly splits into three or four billable segments. And once a message is spilling into four segments, a single MMS can actually be the cheaper send.
Full disclosure: I work for ReadySMS, so I'm going to run the math using our per-segment tiers. But the segment-splitting rules I'm about to walk through are carrier-level facts — they apply no matter who you send through.
The rule everyone forgets: segments, not messages
You don't pay per "text." You pay per segment. And the segment boundary is smaller than people think.
- A plain GSM-7 message fits 160 characters in one segment.
- The moment a message needs more than 160, it doesn't just add one segment — it re-chunks into 153-character pieces (the extra 7 chars per segment go to header data that stitches the parts back together).
- Drop in a single emoji, curly quote, or em-dash, and the whole message becomes unicode. Now your limit is 70 characters per segment (67 for multipart).
That last one is the trap. A 175-character promo copy reads like "one text" in your head. If it's clean GSM-7, it's 2 segments. If it has one 🎉 in it, it's 3 unicode segments. You've silently 1.5x'd the cost of the campaign with a party popper.
If you want the deeper treatment of when to reach for MMS on its own merits, we covered that in SMS vs MMS: When the Extra Cost Is Worth It. This post is narrower: purely the cost crossover.
What an MMS actually costs on ReadySMS
An MMS is billed as a flat unit regardless of length — you can pack ~1,600 characters of text plus an image, and it's still one send. On ReadySMS, an MMS is priced as roughly 3 SMS segments worth of send cost, plus the carrier pass-through applies once per message.
That "3 segments" ratio is the whole story. It means:
- A 1- or 2-segment SMS is always cheaper than an MMS. No contest.
- A 3-segment SMS is roughly break-even with MMS.
- A 4-segment (or longer) SMS costs more than sending the same thing as one MMS.
So the crossover point is between 3 and 4 segments. Anything at or past 4 segments, the picture wins on price — before you even count the higher engagement a visual usually gets.
The worked math (Starter tier, 5,000 contacts)
Let's price a real blast. Say you're on the Starter tier — $0.0155 per segment plus the $0.0045 carrier pass-through per segment, so $0.0200 all-in per segment. You're sending to a 5,000-person opted-in list.
Here's what the same Black Friday promo costs at different lengths:
| Message | Segments | Per-contact cost | 5,000-contact send |
|---|---|---|---|
| "40% off. Code SAVE40. Ends Sun." (GSM-7) | 1 | $0.0200 | $100.00 |
| ~280 chars, clean copy (GSM-7) | 2 | $0.0400 | $200.00 |
| ~280 chars + 🎉 (unicode) | 4 | $0.0800 | $400.00 |
| Same offer as one MMS (image + copy) | ~3-equiv | ~$0.0600 | ~$300.00 |
Look at rows three and four. That single emoji pushed a ~280-character unicode message to four 67-character segments, taking the send to $400. Sending the identical offer as an MMS runs about $300 — a $100 saving on one blast, plus you get an actual product image doing the persuading.
The carrier pass-through matters here too, because it's charged per segment on SMS but once on MMS. Four segments = four pass-through charges. One MMS = one. That's a piece of the gap most people never see itemized. We broke down that line item specifically in The $0.0045 Line Item Most SMS Providers Bake Into Their 'Per-Message' Price.
The unicode tax is the real villain
Notice that the SMS only lost the cost battle because of the emoji. Without it, that 280-character promo was 2 GSM-7 segments at $200 — comfortably cheaper than the $300 MMS.
So before you conclude "MMS is cheaper for us," check whether your copy actually needs to be unicode. Common offenders:
- Emoji — one is enough to convert the whole message.
- Curly quotes and apostrophes — many CRMs and copy-paste-from-Word workflows insert
'(unicode) instead of'(GSM-7). - Em-dashes and ellipsis characters —
—and…are unicode;-and...are not. - Accented characters —
café,piñata, etc.
Swap the smart quotes back to straight quotes, drop the emoji or move it to the very end where it can't fragment the whole thing, and a 4-segment unicode message often collapses back to 2 GSM-7 segments. That's a 50% cost cut with zero change to the offer. Fix the copy before you decide you need MMS.
When MMS wins even after you clean up the copy
Sometimes you genuinely can't get under 3 segments, or the visual does real work. That's when MMS is the right call on both cost and performance:
- Long, detailed offers. Multi-item bundles, tiered discounts, "spend $X get $Y" ladders — this copy runs 400+ characters and lands at 3+ segments even clean. Put it on an MMS.
- Product launches and lookbooks. A product release send where the item is the pitch. A photo outperforms 300 characters describing the photo.
- Anything you'd otherwise cram a link-plus-context into. If the message is "here's the sale, here's what's in it, here's the code, here's the deadline," you're at 4 segments. One MMS carries all of it plus the hero image for less.
- Coupons and QR codes. Barcodes and scannable codes have to be images anyway.
The honest counterpoint: MMS deliverability on 10DLC can be slightly fussier, and not every campaign needs a picture. A one-line flash-sale alert should stay a single SMS forever — it's $100 per 5,000 sends and it works. Don't reach for MMS out of habit. Reach for it when the math or the message earns it.
A simple pre-send checklist
Before any offer-heavy blast, run these four checks:
- Count the segments, not the message. Most send tools show the live segment count as you type. If your platform doesn't, that's a problem.
- Look for unicode. If a short message is showing more segments than the character count justifies, you've got a hidden emoji or smart quote.
- If you're at 3 segments, ask if a visual helps. You're break-even on cost — the image is essentially free upside.
- If you're at 4+ segments, default to MMS. You're paying MMS-plus money for a wall of text either way.
For high-volume senders, this compounds. A store running weekly promos to 20,000 subscribers that accidentally sends everything as 4-segment unicode is burning roughly $1,600/week versus $1,200 on MMS — call it $20,000 a year in avoidable spend, before touching your rate tier. If your volume is climbing, the Standard and Pro tiers drop the per-segment cost further, and it's worth knowing exactly where the tier crossovers sit.
The practical takeaway
The instinct that "MMS is always more expensive" is only true for short messages. The crossover is clean and easy to remember:
- 1–2 segments: SMS is cheaper. Keep it text.
- 3 segments: roughly break-even. Use MMS if a visual helps.
- 4+ segments: MMS is cheaper and usually converts better.
And the biggest single lever isn't SMS-vs-MMS at all — it's killing the accidental unicode that turns a clean 2-segment message into a bloated 4-segment one. Fix the copy first; choose the format second.
If you want to plug your own list size and message length into the numbers, the cost calculator does the segment and tier math for you. Send yourself a test blast, watch the live segment count, and you'll spot your own hidden emoji tax in about thirty seconds.