Slotly — Appointment & Booking System (PHP + MySQL, Self-Hosted) vs. renting SaaS
Self-hosted appointment booking engineered so it can't double-book.
The subscription math
Slotly — Appointment & Booking System (PHP + MySQL, Self-Hosted) — yours
$34.00
one-time · self-hosted · your data, your server
Buy once
Calendly — rented
Standard $10/seat/mo, billed yearly; free tier limited to 1 event type on 1 calendar
[1]
Break-even:
2 months
of Calendly equals the one-time price.
Assumption: Per-seat pricing - calculator assumes 3 staff seats x $10 = $30/mo (Standard, annual billing). The free tier cannot model a multi-service business, and "any available staff" round-robin needs Calendly Teams at $16/seat/mo - Slotly ships round-robin in the one-time price.
How their pricing grows:
Calendly charges per seat, and you add or remove seats directly from account billing as your team changes size.
“From there, you can change your plan, add or remove user seats, and update your payment information.” — read 2026-08-11
What Calendly does that we don't:
Calendly lets you invite teammates into a trial account for free, so a whole team can test paid features together before committing to a plan.
If you need calendars to sync automatically with Google, Outlook, or Office 365, stay with Calendly — Slotly only knows about bookings made inside itself and does not sync external calendars.
Square Appointments — rented
Free plan; Plus $49/mo per location (Premium $149/mo)
[2]
Break-even:
1 month
of Square Appointments equals the one-time price.
Assumption: Free plan covers basics; Plus is $49/mo per location, Premium $149/mo (read 2026-07-22). Note: the $35/mo + $6/person figure on Square pages is Square Payroll, not Appointments.
How their pricing grows:
Square Appointments' Plus and Premium plans charge a flat monthly fee per business location, so a multi-location business pays more as it adds locations.
“With Square Plus and Square Premium, the monthly fee applies to each location you run.” — read 2026-08-11
What Square Appointments does that we don't:
Square Appointments includes unlimited staff calendars on its plans, with no cap on how many employees you can add.
If you need to collect card payments online at the moment of booking, stay with Square Appointments — Slotly only quotes and tracks deposits in admin, it does not process card payments.
Setmore — rented
Free tier; Pro $5/user/month
[3]
Break-even:
3 months
of Setmore equals the one-time price.
Assumption: Per-user; figure shown for 3 staff x $5 = $15/mo. Free tier exists; Slotly is one payment, unlimited staff (read 2026-07-22).
How their pricing grows:
Setmore charges per user, billing each staff member with their own profile as a seat even if that person never logs in.
“Setmore charges per 'user' or by each staff member with their own profile.” — read 2026-08-11
What Setmore does that we don't:
Setmore offers a paid Live Receptionist add-on where a real person answers your business calls around the clock.
If you need to accept online card payments directly through the booking flow, stay with Setmore — Slotly only quotes and tracks deposits in admin, it never processes cards at booking.
Acuity Scheduling — rented
Starter $16/mo billed annually ($20/mo billed monthly)
[4]
Break-even:
3 months
of Acuity Scheduling equals the one-time price.
Assumption: Flat per-account Starter tier; annual billing saves 20%.
How their pricing grows:
Acuity Scheduling's plans are tiered by how many staff or location calendars you need, scaling from a single calendar on Starter up to many more on higher tiers.
“Use separate calendars per employee or location, depending on business needs.” — read 2026-08-11
What Acuity Scheduling does that we don't:
Acuity Scheduling includes a mobile app so you can manage appointments, client details, and payments from your phone.
If you need two-way calendar sync with Google Calendar, Outlook, or iCloud, stay with Acuity Scheduling — Slotly has no calendar sync and only knows about bookings made inside itself.
Savings calculator
SaaS figures use the cited plan price above (see the sources below);
per-seat plans scale by the seat count from the same cited price. This is arithmetic, not a quote.
Also in this category
SimplyBook.me [5]
Basic EUR 11.9/mo billed annually (free tier exists)
Page served EUR prices to our fetch (geo-dependent) - not used in the USD calculator.
How their pricing grows: SimplyBook.me prices by booking volume rather than by seat, bundling a set number of staff providers into one flat monthly fee per tier.
“SimplyBook.me uses booking-volume pricing rather than per-user pricing, with each plan including a set number of staff providers at a single flat monthly fee.”
What SimplyBook.me does that we don't: SimplyBook.me's free plan includes real booking capacity and app access, not just a stripped-down demo.
If you need to collect online payments and deposits directly at booking, stay with SimplyBook.me — Slotly does not process card payments, deposits are only tracked in admin.
Why owning beats renting here
- One payment. No per-month, per-seat, or per-location fees — the license is perpetual.
- Your data stays on your server. Customer records never live in someone else's cloud.
- No plan ceilings. Records, users, and usage are limited by your hosting, not a pricing tier.
- It keeps working if the vendor doesn't. Self-hosted software can't be sunset out from under you.
Fair trade-offs: you host it, you back it up, and updates are yours to apply — see the
product page for honest limitations.
Sources
-
Calendly — price checked 2026-08-04 —
source
“$10 /seat/mo; free plan "1 event type" + "Connect 1 calendar" (verified 2026-08-04)”
-
Square Appointments — price checked 2026-07-22 —
source
“$0/mo per location - $49/mo per location - $149/mo per location”
-
Setmore — price checked 2026-08-02 —
source
“$5/user/month”
-
Acuity Scheduling — price checked 2026-08-02 —
source
“$16/ month”
-
SimplyBook.me — price checked 2026-07-05 —
source
“Basic - 11.9 euro per month (billed annually)”
Competitor prices change — always confirm on the linked page. We only
print figures we could verify on the date shown.