Estimated monthly cost comparison — not just the headline price
Slack and Trello overlap only partly, so check that both cover what you need before comparing cost.
Prices change often — confirm on the vendor's site before buying. Report incorrect pricing →
Quick Take
Slack has the lower estimated monthly cost (~60%)
Based on advertised price plus documented recurring fees, not your exact usage.
Best for Slack
Team messaging and collaboration hub. Free plan has a 90-day message history limit that forces upgra
Best for Trello
Atlassian's visual Kanban board tool. Free plan is limited by Power-Up restrictions, automation caps
Team messaging and collaboration hub. Free plan has a 90-day message history lim...
Advertised
$0
/month
Estimated monthly cost
$8
/month (illustrative)
90-Day Message History Limit
Free plan deletes message access after 90 days. Your team's entire knowledge base disappears quarter...
Per-User Cost at Scale
A 100-person company on Pro pays $875/mo ($10,500/yr). Business+ is $1,250/mo ($15,000/yr). The per-...
Slack Connect External Channels
Connecting with external organizations requires Pro ($8.75/user/mo) minimum. Free plan has no extern...
$7/mo annual
Atlassian's visual Kanban board tool. Free plan is limited by Power-Up restricti...
Advertised
$5
/month
Estimated monthly cost
$20
/month (illustrative)
Power-Up Limit on Free
Free plan allows only 1 Power-Up per board. Need Slack + Google Drive + Calendar? That is 3 Power-Up...
Automation Command Caps
Free: 250 command runs/mo. Standard: 1,000. Premium: 6,000. Complex automations burn through limits ...
View Restrictions
Dashboard, Timeline, Calendar, and Map views require Premium at $10/user/mo. Free and Standard only ...
10MB Attachment Limit on Free
Free plan caps file attachments at 10MB per file. Standard allows 250MB. Teams sharing design files,...
Slack advertises $0/mo. Trello advertises $5/mo.
Slack has 3 documented hidden fees. Trello has 4.
Slack confidence: 83%. Trello confidence: 80%.
| Metric | Slack | Trello | Winner |
|---|---|---|---|
| Advertised Price | $0/mo | $5/mo | Slack |
| Estimated Monthly Cost | $8/mo | $20/mo | Slack |
| Recurring Extra Fees | +$8/mo | +$15/mo | Slack |
| One-Time Costs | $0 | $0 | — |
| # Documented Fees | 3 | 4 | — |
| Pricing Tiers | 4 | 4 | — |
| Affiliate Program | No public affiliate program | No public affiliate program | — |
Slack advertises $0/mo and Trello advertises $5/mo. Slack has 3 documented extra fees (recurring: +$8/mo), while Trello has 4 (recurring: +$15/mo). On these illustrative assumptions, Slack has the lower estimated monthly cost (about 60% less). Your real cost depends on seats and usage — use the calculator for your numbers.
Slack has 3 documented extra fees: 90-Day Message History Limit, Per-User Cost at Scale, Slack Connect External Channels. Recurring fees add roughly $8/mo on top of the $0/mo advertised price.
Trello has 4 documented extra fees: Power-Up Limit on Free, Automation Command Caps, View Restrictions, 10MB Attachment Limit on Free. Recurring fees add roughly $15/mo on top of the $5/mo advertised price.
Choose Slack if: Team messaging and collaboration hub. Free plan has a 90-day message history limit that forces upgra. Choose Trello if: Atlassian's visual Kanban board tool. Free plan is limited by Power-Up restrictions, automation caps. The right choice depends on your team size, usage volume, and which features you need most.
This comparison is compiled from public vendor pricing pages and documentation. It uses illustrative assumptions (see "Cost Comparison Summary"), not your exact seats or usage, and vendor prices change often. Confirm current prices on each vendor's site, and use our calculator with your own usage for a closer estimate. Spotted an error? Email hello@trulycritic.com.
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