Hotel room block and attrition calculator

By Stan MurzynUpdated November 9, 2026

See whether a contracted room block could cost you money.

Three terms

Room block

Rooms a hotel holds for your group on set dates, with a group rate. Guests book with a code until the cutoff date.

Courtesy or contracted

A courtesy block is a hold without an attrition clause. A contracted block is a signed agreement that has one.

Attrition

The share of the block you must fill. Say you must fill 80% of 20 room nights, so 16. If only 12 get booked, you may pay for 4. Terms differ by hotel. Your contract controls.

Your numbers

Attendees

Share who need rooms (%) People per room

Nights in the block

Room nights in your block

Add every night in the contract. 50 + 100 + 50 is 200.

Share of the block you may leave unfilled (%)

If your contract says you must fill 80%, type 20.

Expected pickup (%)

Average rate per night ($, optional) Room nights you need (optional)

Runs in your browser. Closing the page clears your entries.

Your numbers, step by step

Enter attendees and the share who need rooms to start.

Questions to ask the hotel

What is the cutoff date for guests to book at the group rate?
What are the attrition and cancellation terms?
Can the block be reduced, and by when?
Is the group rate guaranteed, and for which nights?
How will you report pickup, and how often?
Are there any concessions or rebates tied to pickup?

What is attrition in a hotel room block?

It's a clause in a contracted block. It sets how many of the blocked rooms you must fill, and you may pay for the unused ones if you fall short.

How do I work out my minimum?

Take your block and subtract the share you may leave unfilled. A 200 room-night block with 20 percent allowed unfilled has a minimum of 160. Your contract may count it differently.