# How does the height of building calculated?

### How does the height of building calculated?

This tall building height  calculatoris  developedto assist in determining tall building heights when only the story count is known. The calculator is divided into three categories representing the three major functions  represented in tallbuildings;
(i) Office
(ii) Residential/Hotel
(iii) Mixed-use or when the function  unknown

The calculator will provide an approximate height for a single tall building, but as tall building characteristics vary significantly with location, structural material, form, profile, etc, in some  instances estimates will vary considerably with actual building height. As such, the calculator is best utilized to determine heights in multiple building / statistical studies, where there are many unknown building heights. In these instances the greater number of buildings examined will reduce any overall variations.

The calculator does not include any factors for spires or any other major projections at the roof plane, due to the wide ranging tnature of hese.

The height calculator is never utilized by the CTBUH to determine any building heights as part of the CTBUH tall building database i.e. all published heights within the CTBUH database are accurate, confirmed heights according to published data.

Height Calculator Assumptions

OfficeResidential/hotelFunction Unkown or Mixed-Use1
floor-to-floor height (f)3.9m3.1m3.5m
Entrance lobby level floor-to-floor height2.0f = 7.8m1.5= 4.65m1.75f = 6.125m
Number of mechanical floors above ground (excluding those on the roof)s/20 = One mechanical floor every 20 storiess/30 = One mechanical floor every 30 storiess/25 = One mechanical floor every 25 stories
Height of mechanical floors2.0f = 7.8m1.5= 4.65m1.75f = 6.125m
Height of roof-level mechanical areas / parapets / screen walls22.0f = 7.8m2.0f = 6.2m2.0f = 7.0m
Key

H= Building height
f = Typical occupied floor-to-floor height
s = Total number of stories3

 Useable Floors Entrance Lobby Mechanical Floors Roof

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1Mixed-use assumptions derived from the average values between office and residential/hotel figures.

2Figures do not assume spires or other major projections at the roof plane.

3The number of stories should include the ground floor level and be the number of main floors above ground, including any significant mezzanine floors and major mechanical plant floors. Mechanical mezzanines or penthouses should not be included if they have a significantly smaller floor area than the major floors below. CTBUH floor counts may differ from published accounts, as it is common in some regions of the world for certain floor levels not to be included (for example, the level 4, 14, 24, etc in Hong Kong).

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1. Calculating the height of an office tall building where only the number of stories is known
 Number of stories (known) = s Assumed floor-to-floor height = f = 3.9m Factor for increased ground level floor-to-floor heightAssuming the entrance lobby floor-to-floor height is 7.8m, the factor will be an additional 7.8 minus (–) 3.9 = 3.9m(e.g. discounting the 3.9m of the ground level floor-to-floor height that has already been counted). Factor for increased mechanical levels floor-to-floor heightAssuming the mechanical levels are 7.8m high, the factor will be an additional 7.8 minus (–) 3.9 = 3.9m per mechanical floor(e.g. discounting the 3.9m of the mechanical floors that have already been counted). The number of mechanical floors is calculated by the total number of floors divided by 20 = s/20 Factor for roof level mechanical systems / parapets / roof featuresAssume this is an additional 7.8m in height (there is no need to discount any stories as roof level mechanical systems / parapets / roof features are not included in the figure for total story count).Height of building = number of stories x floor-to-floor height = 3.9s+ Factor for increased ground level floor-to-floor height = 3.9m+ Factor for increased mechanical levels floor-to-floor height = 3.9m x (s/20)+ Factor for roof level mechanical systems / parapets / roof features = 7.8m Final formula for calculating the height of an office tall building: . 60 Story Office Building

2. Calculating the height of a residential/hotel tall building where only the number of stories is known
 . Number of stories (known) = s Assumed floor-to-floor height = f = 3.1m Factor for increased ground level floor-to-floor heightAssuming the entrance lobby floor-to-floor height is 4.65m, the factor will be an additional 4.65 minus (–) 3.1 = 1.55m(e.g. discounting the 3.1m of the ground level floor-to-floor height that has already been counted). Factor for increased mechanical levels floor-to-floor heightAssuming the mechanical levels are 4.65m high, the factor will be an additional 4.65 minus (–) 3.1 = 1.55m per mechanical floor(e.g. discounting the 3.1m of the mechanical floors that have already been counted). The number of mechanical floors is calculated by the total number of floors divided by 30 = s/30. Factor for roof level mechanical systems / parapets / roof featuresAssume this is an additional 6.2m in height (there is no need to discount any stories as roof level mechanical systems / parapets / roof features are not included in the figure for total story count).Height of building = number of stories x floor-to-floor height = 3.1s+ Factor for increased ground level floor-to-floor height = 1.55m+ Factor for increased mechanical levels floor-to-floor height = 1.55m x (s/30)+ Factor for roof level mechanical systems / parapets / roof features = 6.2m Final formula for calculating the height of a residential/hotel building: . 60 Story Residential/Hotel Building

3. Calculating the height of a mixed-use tall building or where the function of the building is unknown and the number of stories is known

 . Number of stories (known) = s Assumed floor-to-floor height = f = 3.5m Factor for increased ground level floor-to-floor heightAssuming the entrance lobby floor-to-floor height is  6.125m, the factor will be an additional  6.125 minus (–) 3.5 = 2.625m(e.g. discounting the 3.5m of the ground level floor-to-floor height that has already been counted). Factor for increased mechanical levels floor-to-floor heightAssuming the mechanical levels are  6.125m high, the factor will be an additional 6.125 minus (–) 3.5 = 2.625m per mechanical floor(e.g. discounting the 3.5m of the mechanical floors that have already been counted). The number of mechanical floors is calculated by the total number of floors divided by 25 = s/25. Factor for roof level mechanical systems / parapets / roof featuresAssume this is an additional 7.0m in height (there is no need to discount any stories as roof level mechanical systems / parapets / roof features are not included in the figure for total story count).Height of building = number of stories x floor-to-floor height = 3.5s+ Factor for increased ground level floor-to-floor height = 2.625m+ Factor for increased mechanical levels floor-to-floor height = 2.625m x (s/25)+ Factor for roof level mechanical systems / parapets / roof features = 7.0m Final formula for calculating the height of a mixed-use or function unknown tall building: . 60 Mixed-Use or Function Unknown Building