Team messaging
What does 400 Slack seats cost in 2026?
At list pricing on the Business+ plan ($15/seat/mo, billed annual), 400 seats run $6,000/month or $72,000/year. Real invoices vary with negotiated discounts, add-ons, and mid-cycle changes.
Monthly
$6,000
Annual
$72,000
Typical shelfware (25%)
$18,000/yr
All Slack plans at 400 seats
| Plan | Per seat/mo | Total monthly | Total annual |
|---|---|---|---|
Pro Unlimited history, integrations | $8.75 | $3,500 | $42,000 |
Business+ SSO, compliance exports | $15 | $6,000 | $72,000 |
Enterprise HIPAA, data residency, unlimited workspaces | $22 | $8,800 | $105,600 |
Source: Slack pricing page. List price, USD, annual billing where offered.
The number nobody puts on the pricing page
SeatMap.AI's Shelfware Index shows the median Slack team runs at 25% inactive seats. On a 400-seat Business+ plan, that's $18,000/year paid for seats that never showed up.
What a real Slack audit at this size looks like
- Median active-user rate
- 74%
- Shelfware Index benchmark for Slack teams this size.
- Dormancy window
- 90 days
- How long a seat can sit idle before it counts as ghost.
- Hidden cost we flag
- Guest single-channel seats billed as full seats on Business+.
Slack seats are usually reclaimed in the same day the audit runs — the 24-hour warning queue rarely gets challenged because dormant seats correlate almost 1:1 with departed contractors.
"Once we saw the actual last-active-in-Slack timestamp per user, the reclaim call was obvious."
Read the full breakdown in case studies or see the live weekly benchmark on the Shelfware Index.
Other team sizes
5 seats10 seats15 seats20 seats25 seats40 seats50 seats75 seats100 seats150 seats200 seats250 seats300 seats500 seats750 seats1000 seats2000 seats3000 seats5000 seats