24 hours per day vs 24 hours a day

Both '24 hours per day' and '24 hours a day' are correct and able to be used in English. They are interchangeable and convey the same meaning.

Explained by Vince
Editor at TextRanch

Last updated: August 22, 2024

24 hours per day

This phrase is correct and commonly used in English.

This phrase is used to indicate that something happens continuously throughout the day, without interruption.

Examples:

The convenience store is open 24 hours per day.
The hospital operates 24 hours per day.
The security cameras monitor the area 24 hours per day.

Show examples from the web [+]

Ability to work on one site 24 hours per day for 7 days.
Ability to work 24 hours per day on more than one site for 10 days.
Hence, many are 'on call' 24 hours per day, 7 days a week, 52 weeks of the year, with little or no opportunity to enter paid employment or to enjoy a normal social life.
the emergency must be documented by the veterinary surgeon on call 24 hours per day, 7 days per week;
is designed to be operational 24 hours per day and 7 days per week;
2.1. the emergency must be documented by a veterinary surgeon, on call 24 hours per day, 7 days per week,
the transport operation must be authorised by the competent authorities who must be reachable 24 hours per day, 7 days per week;
2.3. the transport must be authorised by the competent authorities, who must be contactable 24 hours per day, 7 days per week,
An emergency must be documented by a veterinary surgeon on call 24 hours per day, 7 days a week.
The Minister for Industry, in the hearing duly organised by Mr Baron Crespo, gave a precise account of the figures: 100 million employees working 24 hours per day.
Abdullah Ocalan's ordeal has included six years of solitary confinement, sensory deprivation, inadequate medical treatment, 24 hour surveillance and mandatory 24 hours of light per day.
And a man like Guillaume needs more than 24 hours of protection per day.
That is because the provision itself was essentially declaratory, so employees still have the right under the working time directive to a minimum uninterrupted rest period of 24 hours per seven-day period, in addition to the 11 hours daily rest.
Dosage adjustments, if indicated, should occur at intervals of not less than 24 hours and in dosage increments of 1 mg per day.
Therefore, this specific regimen with concomitant administration with high-dose cytarabine (2 g/ m2 per day) by continuous infusion over 24 hours is not recommended.
Therefore, this specific regimen with concomitant administration with high-dose cytarabine (2g/ m2 per day) by continuous infusion over 24 hours is not recommended.
Daily rest at home must be a minimum of 12 consecutive hours per 24-hour period.
The minimum daily rest away from home shall be eight consecutive hours per 24-hour period.
Exposure time should be six hours per day.
The exposure period should be at least six hours per day.

Alternatives:

24 hours a day
24/7
around the clock
all day and night
day and night

24 hours a day