How to calculate the cost of an SMS campaign
The cost of an SMS campaign does not depend on how many people you contact, but on how many SMS are actually sent. That is the nuance that catches most business owners out: a slightly too long message doubles the bill without warning anyone.
The full formula:
Cost = contacts x campaigns per month x message segments x pack unit price
A worked example
Take a base of 800 contacts, 2 campaigns a month and a pack of 5,000 SMS at 0.089 euro per unit.
If your message fits in a single SMS, you send 1,600 SMS and pay 142 euros. If the same message weighs two SMS, you send 3,200 and pay 285 euros. The text did not change meaning, only length, and the monthly budget doubled.
What this calculation will not tell you
The cost is certain, the revenue is not. The in-store return rate after an SMS is measured by no public study, for no local retail sector. That is why the generator shows a range rather than a single number, and lets you set the assumption yourself.
How many characters fit in an SMS?
An SMS is not a free text field, it is a technical frame. Its capacity depends on the alphabet used, defined by the 3GPP TS 23.038 specification, with long message splitting covered by TS 23.040.
| Alphabet | Single message | Per part when split | What triggers it |
|---|---|---|---|
| GSM 7-bit | 160 characters | 153 | The normal case for plain text |
| Unicode | 70 characters | 67 | A single out-of-table character is enough |
Accented letters cost nothing
This is the most widespread myth, and it is false. The characters é, è, à, ù, ì, ò, Ç, É, ä, ö, ü, ñ are all in the base GSM table. A properly accented French message still fits in 160 characters.
The characters that really switch the encoding
Two families are expensive, and both go unnoticed.
Characters from the extension table count as two on their own: ^ { } \ [ ~ ] | and the euro sign. Writing "10 €" instead of "10 euros" therefore uses one more character than you think.
Out-of-table characters switch the whole message to Unicode, and capacity drops at once from 160 to 70. The usual culprits are emoji, the œ ligature, and above all curly quotes and typographic apostrophes pasted from a word processor. A character invisible to the eye can double your bill: the counter above tells you which one.
How much does an SMS cost by volume?
SMS are bought in packs, and the unit price falls as volume rises. Here is the public grid.
| Pack | Unit price | Pack cost |
|---|---|---|
| 1,000 SMS | 0.100 € | 100 € |
| 5,000 SMS | 0.089 € | 445 € |
| 10,000 SMS | 0.069 € | 690 € |
| 25,000 SMS | 0.065 € | 1,625 € |
| 50,000 SMS | 0.062 € | 3,100 € |
| 100,000 SMS | 0.059 € | 5,900 € |
Above 100,000 SMS a month the rate is no longer public and moves to a quote. The full grid is on the pricing page.
How many customers make a campaign pay for itself?
This is the most useful question, and the answer is a simple division: campaign cost divided by your average basket.
A 142 euro campaign with a 12 euro average basket pays for itself at 12 returning customers. The same campaign, with a 45 euro basket, pays for itself at 4. The average basket is therefore the figure that moves the result most, well ahead of the return rate.
That threshold rests on no assumption at all, which is why the generator shows it first and labels it an exact calculation rather than an estimate.
You have your message and your budget. Now it needs sending.
Up Review sends your SMS campaigns from your customer file, with consent and opt-out handled automatically.
When can you send a commercial SMS?
The hours
Contrary to what is often written, no French statute sets a time window for commercial SMS. The rule comes from the Business Messaging charter of af2m, the association of the four French mobile operators, in force since 1 March 2026: promotional messages allowed between 8am and 9:30pm, recommended Monday to Saturday, tolerated but not recommended on Sundays and public holidays.
The old rule, 8am to 8pm and nothing on Sundays, is no longer the one that applies. Functional messages, such as an appointment confirmation or an order-ready notice, are not covered by those hours.
Consent
For consumers, prior consent is mandatory. It must be freely given, specific, informed and unambiguous, and a pre-ticked box does not count. Every message must identify the sender and allow opting out by a simple, free means. These rules are set out by the CNIL, whose guidance on commercial prospecting was updated on 10 June 2026.
The same consent covers SMS and RCS: you do not have to ask your customers again to move from one channel to the other.
To compare SMS with its successor, which supports images and buttons, try our RCS message generator: it works out the uplift RCS must deliver to beat SMS on your own base.
To go further, see how Up Review sends your SMS campaigns, or read our complete guide to bulk SMS marketing.