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Calclating gradient

marco67marco67 Posts: 91
edited May 2007 in Road beginners
Hi all, I hope this is the correct place to post this question.
Can someone help me with calculating gradients from modern % to the good old fashioned 1 in 4 for example.
I sat watching the Giro yesterday afternoon, now I know the Zoncolan was steep but how would 22% translate.
I'm sure I covered this in maths at school, but that was a long time ago and i'm not even sure if I was listening anyway.

Ciao Marco
Ciao Marco


  • Mosschops2Mosschops2 Posts: 1,774
    To get from % to x in y.....

    you need to divide 100 by %. For example,

    22%: 100 / 22 = 1 in 4.5
    10%: 100 / 10 = 1 in 10
    5%: 100 / 5 = 1 in 20


    Basically 20% means "20 in 100", which is the same as "one in five".

    Hopefully that makes sense, and is correct!!

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  • benjusbenjus Posts: 27
    Yes, it is school maths. Gradient as a ratio (e.g. 1 in 4) is just another way of saying the fraction on quarter (1/4), which is another way of saying 25%.

    To convert a ratio to a percentage, multiply the first number by 100, then divide it by the second number (e.g. 1 in 4 = (1 * 100) / 4 = 25%)

    To convert a percentage to a ratio, divide 100 by the percentage to give the ratio. For example, 22% gives 100/22 which is 4.54, so the ratio is "1 in 4.54". You could then round it to "1 in 4.5" or "1 in 5".
  • marco67marco67 Posts: 91
    Thanks Mosschops2
    It makes sense, whether brain will function to calculate that when I hit the bottom of the hill remains to be seen.

    Ciao Marco
    Ciao Marco
  • oldwelshmanoldwelshman Posts: 4,733
    Well I watched the race last night and they said it was 22 degrees which I think not [:D]
    If it was 22 degrees then from tirgonometry. 1/tan22 gives 2.5 which gives 1:2.5 or 40% so I guess they meant 22% [:D]

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  • Mosschops2Mosschops2 Posts: 1,774
    No worries marco67.

    (Also, I think you meant to write "Calcliating" for the title!!! [;)])

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  • Mr Dood L DooMr Dood L Doo Posts: 128
    Remember that the divisor in this fraction is not the horizontal distance, but is instead the incline distance. Counter-intuitive but that's how it goes.

    The old 1 in 4 was based on the horizontal distance so really 1 in 4 equates to 24.3 degrees in new money.

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