If you're planning a budget around 80,000 outbound segments a month and you've penciled in "$0.016 per segment because we hit the Growth tier," your forecast is wrong. Not by a huge margin — but by enough to matter when you're presenting a number to a client or a CFO who's going to hold you to it.
Full disclosure: I work for ReadySMS, so I'm the one who has to explain this when someone opens their invoice expecting one number and finds another. The confusion is always the same. People treat the Growth rate like a switch — flip past 50,000 and every segment reprices. That's not how tiered pricing works here, and understanding why is the difference between a forecast that survives contact with reality and one that doesn't.
The mechanic that trips everyone up: tiers are marginal, not retroactive
ReadySMS pricing has two tiers on the per-segment rate, plus a flat carrier pass-through that sits underneath everything:
| Tier | Volume / month | Per segment | + carrier pass-through | All-in |
|---|---|---|---|---|
| Standard | 0–50,000 | $0.02 | $0.0045 | $0.0245 |
| Growth | 50,000+ (automatic) | $0.016 | $0.0045 | $0.0205 |
The Growth rate applies to segments past the 50,000 line — not to the whole month. This is exactly how graduated income tax brackets work, and it's why nobody's entire salary jumps a bracket when they get a raise. Your first 50,000 segments in a calendar month bill at $0.02. Segment number 50,001 onward bills at $0.016.
So at 80,000 segments, you don't have 80,000 segments at $0.016. You have 50,000 at $0.02 and 30,000 at $0.016. Two different rates, one bill.
One nice thing worth saying up front: the Growth drop is automatic. You don't request it, you don't sign up for a plan, you don't call anyone. Cross 50,000 in a calendar month and the cheaper marginal rate kicks in on its own. (If you want the full breakdown of when that crossover triggers and how to plan send calendars around it, we wrote that up separately in the crossover volume planning post.)
The actual math at 80,000 segments
Let's do it in full, carrier fee included, because the carrier pass-through doesn't tier — it's a flat $0.0045 on every single segment regardless of volume.
First 50,000 segments (Standard rate):
- Per-segment: $0.02
- Carrier: $0.0045
- All-in: $0.0245
- 50,000 × $0.0245 = $1,225.00
Next 30,000 segments (Growth rate):
- Per-segment: $0.016
- Carrier: $0.0045
- All-in: $0.0205
- 30,000 × $0.0205 = $615.00
Total for 80,000 segments: $1,840.00
Now divide that back out to find your true blended rate:
$1,840.00 ÷ 80,000 = $0.023 per segment, all-in.
Compare that to what people assume they'll pay:
- Naive "we're on Growth" math: 80,000 × $0.0205 = $1,640.00
- Actual blended cost: $1,840.00
- Difference: $200/month you didn't budget for
That $200 gap is the retroactive-pricing myth in dollars. It's not a rounding error — it's a line on your P&L that either you eat or your client's bill absorbs.
Why the blended rate keeps moving as you scale
Here's the part that makes forecasting genuinely tricky: your blended rate isn't a fixed number even within the Growth tier. It slides toward $0.0205 as your volume climbs, because the fixed 50,000-segment slug at the higher rate becomes a smaller and smaller fraction of the total.
| Monthly segments | Standard portion cost | Growth portion cost | Total | Blended all-in |
|---|---|---|---|---|
| 60,000 | $1,225.00 | $205.00 | $1,430.00 | $0.02383 |
| 80,000 | $1,225.00 | $615.00 | $1,840.00 | $0.02300 |
| 120,000 | $1,225.00 | $1,435.00 | $2,660.00 | $0.02217 |
| 250,000 | $1,225.00 | $4,100.00 | $5,325.00 | $0.02130 |
| 500,000 | $1,225.00 | $9,225.00 | $10,450.00 | $0.02090 |
Notice the pattern. At 60,000 segments you're barely into Growth, so your blended rate is $0.0238 — closer to the Standard all-in of $0.0245 than to the Growth floor. At half a million, you've diluted that fixed first-tier cost enough to sit at $0.0209, almost touching the $0.0205 marginal rate.
The practical takeaway: the closer you are to the 50,000 line, the more your blended rate looks like Standard pricing. If you're at 55,000 segments, don't budget as if you're getting the Growth rate on everything — you're barely getting it on anything.
How to forecast this without a spreadsheet fight
The formula is simple enough to keep in your head. For any monthly volume V above 50,000:
`` Total = (50,000 × $0.0245) + ((V − 50,000) × $0.0205) = $1,225 + ((V − 50,000) × $0.0205) Blended = Total ÷ V ``
For 95,000 segments:
- $1,225 + (45,000 × $0.0205) = $1,225 + $922.50 = $2,147.50
- Blended: $2,147.50 ÷ 95,000 = $0.0226/segment
If math in your head isn't your thing, the ReadySMS cost calculator does the tiering for you — punch in an expected monthly volume and it splits the tiers automatically. But I'd encourage learning the formula anyway, because it's the number you'll defend in a budget meeting, and "the calculator said so" is a weaker answer than showing the two-line breakdown.
What this means for agencies rebilling clients
If you're marking up SMS to clients, the blended-rate slide directly affects your margin — and it moves in your favor as volume grows, but only if you priced against the blended number, not the marginal one.
Say you rebill clients at a flat $0.03/segment. At 80,000 segments:
- Your cost: $1,840.00 (blended $0.023)
- Client revenue: 80,000 × $0.03 = $2,400.00
- Margin: $560.00
If you'd budgeted your own cost at the naive $0.0205 blended rate, you'd have expected $2,400 − $1,640 = $760 in margin — and been $200 short every month, wondering where it went. The tier math is the difference between an accurate margin model and a leaky one.
We went deeper on the margin mechanics of the Standard-to-Growth crossover — including how the breakpoint changes your effective take — in the agency blended margin post. And if you're deciding where to set your rebill markup before clients start auditing the line item, the markup ceiling post is the companion read.
When it's worth talking to us instead of running the math
The Growth tier is automatic and self-serve — there's nothing to negotiate to get it. But there's a volume past which running Growth math stops being the right exercise, because Enterprise pricing is negotiated per deal and isn't published anywhere. I won't quote a number, because there isn't a public one.
The honest signal: if you're consistently sending well into six figures of segments a month, the blended-rate slide flattens out and the marginal $0.0205 dominates your bill. That's the point where a conversation with our deal desk can beat what the public tiers give you. If you want the framing on where exactly that crossover sits, the Growth-to-Enterprise breakeven post lays it out.
The one number to remember
At 80,000 segments a month, your all-in cost is $1,840 and your true blended rate is $0.023 per segment — not $0.016, and not $0.0205. The Growth rate is real and it's automatic, but it only applies to what you send past the first 50,000.
Budget the tiers separately, keep the carrier pass-through in every line (it never discounts), and rebuild the blended number whenever your forecast volume changes — because it moves every time. If you want to sanity-check a specific volume before you commit it to a budget, the pricing page has the tier table and the calculator does the split for you. Forecast the tiers, not the headline.