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Overbooking Math

If your no-show rate is 23%, you should NOT overbook by 23%. The correct answer is 14-16%. Here is why, and the calculator to find your number.

Overbook calibration calculator

Enter your current no-show rate and slot count to find your safe overbook level.

Wrong overbook
23%
Book 25 slots
Correct overbook
15.0%
Book 23 slots
+3
Extra slots to add
~15
Collision days/year
Formula: Safe overbook = no-show rate × 0.65. Collision days are days when attendance exceeds 100% of original capacity, occurring approximately 6% of working days at this calibration.

Why 60-70% of your no-show rate, not 100%

If you overbook by your full no-show rate, you are assuming that no-shows occur at exactly their average rate every day. They do not. No-shows follow a binomial distribution. Some days your attendance is 90% of scheduled, some days it is 110%.

At a 23% no-show rate with 20-slot schedule:

Overbook by 23% (wrong)Book 24-25. On good days: 24-25 patients. Chaos.
Overbook by 15% (correct)Book 23. On good days: 22-23 patients. Manageable.

The 60-70% calibration keeps you within 1-2 patients of capacity on worst-case attendance days approximately 95% of working days. The remaining 5% are collision days requiring triage.

Who overbooking works for

  • +High-volume primary care (20+ slots/day)
  • +Practices with a triage protocol for overflow
  • +Settings with flexible waiting room capacity
  • +Airlines, bus lines, and hotel environments

Who should NOT overbook

  • xBehavioral health and therapy practices
  • xSpecialist appointments with long slot times
  • xSurgical and procedure-based practices
  • xAny setting where overflow cannot be triaged

Alternatives to overbooking

Active waitlist
Fills 30-45% of no-show slots

Lower risk than overbooking. Only fills slots when they actually open.

Same-day scheduling buffer
Converts demand to same-day

Reserve 10-15% of slots for same-day booking. Same-day appointments have very low no-show rates.

SMS reminder program
28-38% rate reduction

Reduce your no-show rate so overbooking becomes less necessary.

Reduce hubSMS remindersPolicy templatesHealthcare calculator

FAQ

Should medical practices overbook?+
Yes, in high-volume primary care environments, calibrated overbooking is a standard and evidence-based practice. The key is calibration: overbook by 60-70% of your no-show rate, not 100%. For specialist practices, behavioral health, and any practice without triage capacity for overflow days, overbooking is generally not recommended.
How do you calculate the right overbook rate?+
Safe overbook rate = your no-show rate x 0.65. For a 23% no-show rate: 0.23 x 0.65 = 15% safe overbook. This keeps you within acceptable service variance - collision days (days when more than expected show up) occur approximately 5-8% of the time at this calibration, which is manageable with standard triage.
What is the risk of overbooking?+
The primary risk is collision days - days when your no-show rate is lower than expected and you are at 115-120% capacity. These occur approximately 5-8% of working days with calibrated overbooking. Practices need a collision protocol: extended hours on predicted high-attendance days, same-day scheduling buffers, or provider backup coverage.