An Ideal Tarp size?

I have tried a few different size rectangular tarps. One I made was too small. I had in my notes from a trip years ago that a 5x7 foot tarp was a bit too small in a driving rain. I'm wondering what size rectangular tarps you have had experience with and how they worked out. Given all other things being equal, I would rather have it be square. Yet there is no sense in carrying extra weight just to make it square. The purpose of my tarp would be to carry it on day hikes/climbs for emergency shelter or bivy and to sleep under in mild weather. Rain is common there, but I find it is usually easy to find a place out of the wind. I know there are some really good tarp-tents manufactured (the SMD Lunar duo looks swell), but there are other reasons I am considering making a rectangular tarp (mostly versatility, but also cost and ease of design/sewing).

I've only tarped with the basic blue plastic grommeted things available at every hardware store, so my size selections were limited to those available -- all rectangular.

I agree, 5' x 7' is too snug. 8' x 10' on the other hand worked perfectly as a solo shelter for me: roomy, dry, and tight enough to use in windy conditions.

For a two-person shelter, 10' x 12' was the size that seemed to work best for me.

I have an 8x10 silnylon tarp which seems to be plenty roomy for one, but it would work for two. Guylines, stakes, and lots of extra tieouts bring the weight to around 24 oz.

I've never made a tarp but I generally use one of two tarps: one 5x8.5 (a poncho/tarp) and the other 8x10.

The smaller works fine in a lean-to configuration but for driving rain I would want to be able to make an A-frame where I could put the edges down to the ground and the 5 foot width doesn't work for that.

My 8x10 I generally pitch with an 8 foot ridgeline. That makes the sides much wides than one person would need. Two fit under there nicely with good protection.

I'm thinking 8x8 would be about optimal for one person. I know you are planning on making it yourself but I just noticed that JacksRBetter.com is having a sale and their 8x8 tarp is going for 79.95.

I have used a 5x8 poncho tarp for this purpose without too much trouble. I.E. for what you describe where it is usually easy to find a place out of the wind, sleeping under in mild weather etc.

Were I planning on tarping in really bad weather and wanted some comfort, take an 8x10. but you *can* do just fine in a 5x8 - it's just if the weather gets bad you don't have a lot of room and have to pitch it pretty low.

to put it in perspective, I take an 8x10 silnylon tarp hiking normally, that goes over my hammock, or I pitch on the ground if there are no trees. The nice part is I can be under it for days in pouring rain and it's like a palace.

But for what you describe (dayhikes, emergency, sleeping under on a superlight trip in probably good weather) I take a 5x8 integral designs silponcho.