Budgeting WhatsApp: the cost per resolved case
Since October, WhatsApp is billed per message. The formula to budget it, three operations worked out with real rates and the levers that bring it down.
On October 1 WhatsApp stopped charging per conversation and started charging per message. In that day’s article we covered what changed and seven adjustments to avoid overpaying.
This one goes a step further: how to turn that change into a number you can put in next year’s budget, with math you can redo using your own data.
The formula
With per-message billing, the unit that matters is no longer the conversation. It is the resolved case: how many messages your business sends, start to finish, to close an inquiry.
Your monthly cost to serve comes from four numbers:
(cases per month × business messages per case − 1,000 free per number) × your market’s service rate
- Cases per month: the inquiries your operation closes on WhatsApp.
- Messages per case: only the ones the business sends. What the customer writes is not billed and never was.
- 1,000 free: the monthly allowance of service messages Meta gives each business number. It does not roll over.
- Service rate: your market’s rate on Meta’s rate card.
Templates your business initiates, such as reminders or notices, are added separately at their category’s rate.
Three operations, worked out
We use the Central America rate, $0.0113 per message, and two scenarios per case: six messages, typical for an untuned flow, and two, what a flow that asks for all the data at once and answers in full achieves.
| Criterion | 6 messages per case | 2 messages per case |
|---|---|---|
| Small operation · 1,500 cases a month | $90.40 | $22.60 |
| Mid-size operation · 20,000 cases a month | $1,344.70 | $440.70 |
| Large operation · 200,000 cases a month | $13,548.70 | $4,508.70 |
The gap between the two columns does not come from negotiating with anyone. It comes from how your agent replies. In the large operation it is $9,040 a month, or $108,480 a year, for the same service.
The market weighs as much as the volume
The same mid-size operation, already tuned to two messages per case, costs very differently depending on the country:
| Colombia $0.0008 per message | $31.20 |
|---|---|
| Mexico $0.0085 per message | $331.50 |
| Central America $0.0113 per message | $440.70 |
| Peru $0.0300 per message | $1,170.00 |
A regional operation that budgets WhatsApp with a single average number is mixing markets that differ by up to 37 times. Budget by country.
The four levers that bring the budget down
1. Messages per case. The biggest lever, and the only one that depends on you alone: replies in one message rather than three bubbles, all the data asked for at once, no filler messages. The details are in the seven adjustments.
2. What does not need WhatsApp, to another channel. WhatsApp is where your customers are, and for that it is worth what it costs. But not everything has to go through it. Telegram does not charge per message: its bot API is free, which is why it works well for the agents your own team uses, such as internal alerts, reports or tasks. The chat on your website does not pay Meta per message either. Every inquiry resolved there stays out of the formula.
3. Ads that open a conversation. When a customer arrives through a Click-to-WhatsApp ad and you reply within the first 24 hours, a 72-hour window opens in which no message is billed. If you already spend on ads, pointing them to WhatsApp makes the service that follows cheaper.
4. Each template’s category. What your business sends on its own initiative is billed by template category. In Mexico, a marketing template costs $0.0397 and a service message $0.0085: almost five times less. Reviewing categories once avoids paying marketing rates for notices that are really service.
The full budget
The message is part of the cost, not all of it. An honest budget for WhatsApp customer service adds three lines:
| Criterion | What it is | How it is calculated |
|---|---|---|
| Meta messages | What Meta bills per delivered message | The formula above, plus templates |
| Platform | Inbox, agents, flows, CRM and metrics | In Shimli, one plan at $139 a month with every feature |
| AI usage | What the agent uses to understand and reply | In Shimli, $49 per 2,450 additional queries |
How Shimli handles it
In Shimli, WhatsApp, Telegram, web chat, Instagram, Messenger, calls, SMS and email arrive in a single inbox, served by the same AI agent. That lets you put each inquiry in the channel it belongs to without your team switching tools.
The agent is set up to reply in a single message and ask for all the data at once, which is exactly what defines the cost per case. You create it by chatting with Shimli’s assistant in under 10 minutes, and adjust it by hand whenever you want. The WhatsApp calculator gives you the number for the budget, and Shimli’s plan is a single one: $139 a month with every feature, plus AI usage based on what you use.
Questions on this topic
- How do I work out what I will pay for WhatsApp each month?
- Multiply the cases you handle per month by the messages your business sends to resolve each one. Subtract the 1,000 free service messages Meta gives each number every month. That result, times the service rate of your market, is your cost to serve. Templates are added separately, by category.
- Which rate applies in Honduras, Guatemala or Costa Rica?
- Central America has no market of its own on Meta's rate card: Honduras, Guatemala, Nicaragua, El Salvador, Costa Rica and Panama fall under Rest of Latin America, at $0.0113 per service message since October 1, 2026.
- How many messages per case is normal?
- It depends on the process, which is why it is worth measuring before you budget. As a reference, a balance inquiry handled without tuning usually takes six business messages, and the same inquiry tuned is resolved in two: one message asking for all the data and another with the full answer.
