On the Size of Font

Just back from SanFrancisco, I was trying to find an address in Montreal.
I had to slow down in order to read the street name. While slowing down, a car almost hit my back bumper! Hope it doesn’t sound familiar but I am sure it happens frequently.

Montreal street- Small street sign

On this Montreal picture, you can barely see the streets signs.

Montreal street names are poorly located and the font size is way too small.
How many car accidents happened as a result of this?
I wonder why city planners do not seem to known the law of font size.
n Montreal, this rule is violated everywhere: billboard signs, parking signs, print documents, etc.
How the heck can someone read the Montreal street signs?
What should be the font size for normal readability?
Angle for viewing font

The answer is: 2 X Tan (0.3 degrees/2) X reading distance

The angle that provides good readability for 95% of the people is 0.3 degrees. For a reader at a distance of 60 cm it results in a font size of 3 mm. For a reader at 50 meters, it is 25 cm or one foot. A good approximation is roughly 1/200 of the distance. Montreal city road planners should learn from SanFrancisco.

SanFrancisco Large street Name

On this picture, you can see there is a much bigger Mason street sign on a green background.
Note that this sign has been added over the small one.
The legibility rules are respected: Mix and San Serif fonts on green background and a size above one foot enough for 50 meters distance readability.

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10 thoughts on “On the Size of Font

  1. Do you think the amount of road signs could have an effect,because if you are looking for a particular street name your eyes have to scan the whole area for the sign as well as concentrating on driving.

  2. If you mean by amount, the number of road signs, yes. It will slow the performance (finding the street). The more you have the more you need to read.

    If you mean the size, no. The bigger size will have a negligible impact from the viewing distance in term of footprint.

  3. Pingback: 10 things to do for the success of your web site- the practitioner view « User Experience and Cognitive Engineering

  4. Quote: “What should be the font size for normal readability? The answer is: 2 X Tan (0.3 degrees/2) X reading distance”

    I am developing a user interface for a control and am applying this formula for font sizes. As this formula seems to apply to a specific font I was wondering how to apply it to a Chinese, Russian or Greek character set.

    Any tips?

  5. in montreal street signs are poorly located…come to italy then, you drive for miles and still don’t know where you are….

    • Good luck trying to get a reply, I still did not receive a response since June 2009.
      Mr. Aubin nor his Readers seem willing to respond to comments or questions.

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