What is a room night?
A room night is one hotel room occupied for one night. Two rooms for three nights make six room nights, no matter how many guests share them. Hotels quote group blocks, count pickup and measure attrition in room nights, so every contract figure of rooms times nights is a room-night figure.
You work in the same unit when you build a rooming list and when you read a hotel contract. For short definitions of the terms, see the room block glossary.
Room night calculator
Enter the rooms, check-in and check-out for each stay. The calculator shows how many rooms are taken each night, the peak night and the total room nights. Add your contracted block per night and it flags the nights that go over it. Nothing you enter leaves your browser.
Peak: 52 rooms on Fri 12 Mar, Sat 13 Mar. 156 room nights in total. 2 nights are over the block.
| Night of | Rooms | Rooms needed each night | Against block |
|---|---|---|---|
| Wed 10 March | 6 | Within block | |
| Thu 11 March | 46 | Within block | |
| Fri 12 March | 52 · Peak | 2 over | |
| Sat 13 March | 52 · Peak | 2 over |
Planned room nights from the dates you enter. What a hotel bills also depends on no-shows, early departures and your contract.
How to calculate room nights
- Nights = check-out date − check-in date. The check-out day is not a night: a guest who checks in on 11 March and out on 14 March stays 3 nights.
- Room nights = rooms × nights. Multiply rooms, not guests. Two guests sharing a room are one room night per night.
- Rooms per night = every room occupied that night, added up. Stays that arrive and leave on different dates each add to the nights they cover.
- Total room nights = the nightly counts added up. It should equal the sum of rooms × nights across stays. If it doesn’t, a date is wrong.
Example: 40 rooms for 11–14 March, 12 rooms for 12–14 March and 6 rooms for 10–12 March. The nights come to 6, 46, 52 and 52 rooms; in total 40×3 + 12×2 + 6×2 = 156 room nights.
How many rooms to block
Start from the guests who need a bed, not the invitation list. Divide them by how many share a room, per room type, and round up.
Then lay arrivals and departures over each night. The rooms needed on a night are the rooms occupied that night, and the peak night is where the block is tightest. Contracts usually set one number per night, so a block sized on the peak leaves rooms empty on the shoulder nights, and that is where attrition starts. If you can, ask for a block that follows your arrival curve instead of a flat number; the attrition guide covers the clauses.
Leaving a margin for late additions makes sense, but size it against your contract’s cut-off and shortfall terms. There is no standard percentage.
Room nights in Excel
Put rooms, check-in and check-out on each row (columns B, C and D). Nights in column E are =D2-C2. Total room nights:
=SUMPRODUCT(B2:B50, E2:E50)To count the rooms taken on one night, write that night’s date in G2 and use:
=SUMIFS($B$2:$B$50, $C$2:$C$50, "<="&G2, $D$2:$D$50, ">"&G2)Fill it down next to the night dates and the peak night is =MAX(H2:H30). The same formulas work in Google Sheets.
If you’d rather not build it, the room nights sheet in the free rooming list template does this. Enter the first night and it shows, for 21 nights, how many rooms of each type are taken and the difference against your contracted block.
Common mistakes
- Counting the check-out day as a night. 11–14 March is three nights, not four.
- Counting guests instead of rooms. Two guests in a twin are one room night each night.
- Sizing the block on the average. Read the block against the peak night; on an average you run out of rooms on that night.
- Forgetting the shoulder nights. Guests who arrive a day early or leave a day late fall outside the block.
- Mixing planned and actual nights. See below.
Planned, actual and billable room nights
The figures on this page are planned room nights, worked out from the dates on your list. The nights a guest really stayed (actual) and the nights you pay for under the contract (billable) are different numbers; no-shows and early departures pull them apart. The attrition guide walks through all three with an example, and the rooming list guide covers how to build the list itself.