# Standing distance for A4 snellen chart?

Hey guys, I have a question about the snellen chart. I have found two snellen charts online which can be printed on A4 size paper. But one of them says 10 feet chart and other says 2.8m/9feet measuring distance.

One of them mentions a "formula i.e -measure the height of the letter E (first line, 20/200) in millimeters. Then, divide the value of this measurement by 88. Finally, multiply it
by 6. The result shows the distance at which you must be placed, in meters. E.g. (42/88) x 6 = 2.8 m/9ft.

By using this formula both the charts printed on a4 size paper measures the same. The size of " big E" is same on both charts. If anyone has used home printed a4 charts please suggest how do you measure the distance.

Thanks

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I think it is most important that you stand the same distance all of the time, and control your lighting. So I would suggest pick one and stick to it. Also keep in mind that while more convenient, a 10 foot chart is over all less accurate than a 20 foot chart. But the point it having a means to gauge improvements and either will work for that.
Probably more than you bargained for but I just did a video on measuring that might help you as you get goingâ€¦ https://youtu.be/QyF5J6-BJZI

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I think it is most important that you stand the same distance all of the time, and control your lighting. So I would suggest pick one and stick to it.

• That was my actual questionâ€¦ they both are ment to be 10ft charts, but one says 10ft on it and has different set set of lines and other one is â€śmeant to be 10ftâ€ť too but has instructions that when printed on A4 paper ( because printers can be defaulted to different settings etc) just to make sure the right standing distance one uses the above mentioned formula. So I am confused because as the â€śEâ€ť on both charts measure the same in height does it mean that after printing I use the above formula in order to get the correct distance. Because the difference is of aprox 1ft.
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The 9ft (2.8m)chart and the formula I mentioned in my initial post is the chart as on EM wiki.

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I understood your original post when I responded. And, I stand by my response. Usually we stand at the distance the chart indicates. Though it doesnâ€™t surprise me there is no discernable difference in the point size on the font for at least some of the lines. At a difference of a foot for chart distance I imagine the letter size is so close to the same it is difficult if not impossible to measure the difference.
Personally I would pick the farther, 10 foot distance, because being a little harder on your measurements is a good choice over all. Consistency is the most important element of your measurements. Donâ€™t over stress the little details, like what turns into fractions of millimeters over a distance. As long as you use the same chart at the same distance in the same light conditions, you will succeed in tracking your vision progress.

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Maybe I missed something but are you only measuring the large E? I would only consider the 20/20 to 20/40 lines as thatâ€™s where you will likely be measuring with correction.

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The formula given to determine the distance of your chart requires the length of the large E as its input. By manipulating the scale of the pdf printout, you can change the distance of your chart.

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I understand that. I am just saying I would double check the much smaller letters. I have little faith in my printer, but yours is probably fine.

And as earlier said by @Lloydmom, consistency is the important part. Distance and lighting being key elements.

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@preetgurpreet, I guess you printed this Snellen.

These lines are supposed to be scaled properly like an optoâ€™s Snellen.
If you printed this out in original size (not with â€śfit to pageâ€ť, etc), then the letter E is 42mm tall and youâ€™ll have to stand at 2.8m from it (at 286.36cm to be precise).
If the letter E is not 42mm, then use the formula to get the distance to use. (e.g. 44mm tall letter E = reading from 3metres; 40mm tall letter E = reading from 2.72metres, and so on)
With the 3 or 6 m Snellens, 5 or 10 cms do not really matter. The ultimate goal is not â€śjust to be able to read itâ€ť, but to see the letters clear and sharp.

This is a 6m Snellen:

If you print it out correctly, the 1cm mark should measure 1cm exactly and then youâ€™ll read it from 6m.
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I like this 6m chart. The 1cm scale line is ideal. Thanks for posting as I hadnâ€™t seen this.

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Thanks for the replyâ€¦ exactly the explanation I was looking for.

Thanks everyone for your input. If was measuring myself it wouldnâ€™t have been a problem standing at either 10 or 9 ft, but I use this to measure my 6 year old and being at 9 or 10ft makes a huge (almost a line) difference for him and when he reads a 9ft he can almost clear one whole line, which is like a confidence booster for him. I oviously donâ€™t want to â€ścheatâ€ť too by making him standing at closer distance ( if 9ft is not the correct distance). That was the sole reason to get the distance clear. Thanks to all of you who took time to respond back. Thanks

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