Human Scale
Is the set of physical quantities, and quantities of information, characterizing the human body, its motor, sensory, or mental capabilities, and human social institutions.

Humans interact with their environments based on their physical dimensions, capabilities and limits. The field of anthropometrics (human measurement) has unanswered questions, but it's still true that human physical characteristics are fairly predictable and objectively measurable. Buildings scaled to human physical capabilities have steps, doorways, railings, work surfaces, seating, shelves, fixtures, walking distances, and other features that fit well to the average person.

Humans also interact with their environments based on their sensory capabilities. The fields of human perception systems, like perceptual psychology and cognitive psychology, are not exact sciences, because human information processing is not a purely physical act, and because perception is affected by cultural factors, personal preferences, experiences, and expectations. So human scale in architecture can also describe buildings with sightlines, acoustic properties, task lighting, ambient lighting, and spatial grammar that fit well with human senses. However, one important caveat is that human perceptions are always going to be less predictable and less measurable than physical dimensions.

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Da Vinci was one of the first persons in establishing the perfect proportions of the human being. He created the Vitruvian Man which is based on the correlations of ideal human proportions with geometry described by the ancient Roman architect Vitruvius.

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Throughout the years architects have develop the ability of creating spaces according to the human scale. Spaces can´t be neither too big nor too small because people won´t feel comfortable in it. Also there has been established certain general rules so elements like stairs and doors have similar measures that are according to the human scale.

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Most of the times, when architects design any building in their computers, or even in sketches, they add a person into the drawing. When the person is added it instantly give the design the feeling of reality. So when people see the drawing they can feel some sort of connection and can locate themselves into the building.