Converting ratios into percentages

[DNgroundworks]

Hi all just wondering wether my calculations are wrong or the sums on the drainage section are wrong (probably me)

to convert 1:4 in to a percentage i would do 1/4*100 which results in 25 so its %25 - obvious i know.

I was looking at the first page on the drainage section and it says that "1:60 or 16%......"

Going off the simple calculation that ive done - which could be wrong, would it not be 1/60*100 = 1.6% ?? instead of 16%Or am i completley wrong?

Only reason i think the input mode on a pipe laser ive just bought is in percentages rather than ratios, i havent received it yet though and i was doing some sums to save time on site.

Regards Dan

[Bob_A]

I reckon you are right and there is a typo in the drainage section.

By my reckoning 16% is actually 1:6.25

[lutonlagerlout]

just be careful you dont get percentages mixed up with degrees dan
i use a winkelfix for finding pitches on roofs
angle finder
they are idiot proof for finding angels (handy for me)
regards LLL

[DNgroundworks]

ahh rite but is a degree not represented with a little circle aboce the number?

So on the drainage section on this site, were it states 1:60 = 16% is that 16 percent fall or 16 degrees?

[DNgroundworks]

Also on the screen of the laser, it is represented as x% and not the degree sign so maybe it is percent?

Im getting good at confusing myself lol:p

[sjs]

hi all, newbie so bare with me. have bin spyin on you lot for a while tho

dn your laser will deffo work in a percentage thats standard fare. and your workin out seems spot on to me mate.

ste

[cookiewales]

keep up the good allways room for some more brains and daft uns

[Injured]

LLL, How many 'ANGELS' does it find for you?? or did you mean angles??

Just wondering cos I could do with a couple of angels myself lol :p

[lutonlagerlout]

well spotted injured
looks like i am having a *blonde* day
1:60 to me is having 1 metre rise or fall for every 60 m horizontally
i use a dumpy every week and it quite easy in practise
sort of....
LLL

[GB_Groundworks]

i'm blonde then again you might be right haha

Dan, is it one of those bore lasers that fits into the middle of the pipe and you line the next section up of that?

we use an automatic(dumpy) level and work out manually or use a dual grade laser, i find the leica automatic the quickest and easiest to use though.

googles a pretty good calculator you know

if you type in like "2 foot in cm" it gives you the answer

or "15lbs in kg"

not sure it does ratios though

http://www.google.com/intl/en/help/features.html#calculator

gi

[Tony McC]

Can someone give me a URL for the error? I'll take a look at it and get it fixed.......

[DNgroundworks]

erm i would but i dont know how! i just know it as the first page of the drainage section

[Bob_A]

I think this is it
http://www.pavingexpert.com/drainage.htm
Scroll down half way down the page to the writing by the pink triangle.

[Tony McC]

OK: found it.

It's more of an unfortunate juxtaposition rather than a genuine error. The text runs thus....

Gradients are expressed in a number of ways, including Ratios [1 in 60 or 1:60] and Percentages [16%]

...which I intended to provide examples of the various ways of expressing gradients. It should not be read that 1:60 *is the same as* 16%.

I should have thought more about the potential for confusion that arises from using the same numerals in that sentence. I'll change the text to make it a little clearer.

[Tony McC]

Anyway, back to the original problem, of how to convert between percentages and ratios.

Let's say the gradient is given as a percentage and completely out of the air, I'll pluck the value 16%

If I put "16" into the old calculator, and then press the 1/x (inverse) button, this returns the value 0.0625, which is multiplied by 100 to remove the 'per cent', and so becomes 6.25 which in ratio terms is 1 in 6.25. The 1/x button acts to divide 1 by whatever value has been entered, so in this example, 16 INV becomes 1 ÷ 16.

To go t'other way, from ratio to percentage, simply input the ratio denominator (the big number) and press 1/x (or perform the calculation 1 ÷ denominator) and this returns the value, 0.16 which is 16 parts per hundred or, as we more commonly say, 16%.

Simples!


Afterthought: some calculators use the notation X¯¹ (x to the minus 1) rather than 1/x. It's the same thing



Edited By Tony McC on 1257881449