copper tubing size

I read something that said you have to subtract 1/8" to get the ID of copper tubing. If that's true, does that mean I need to look at getting some 5/8" tubing? Also, how hard is copper tubing to bend? Can I do it with moderate effort or am I going to have to eat some spinach beforehand?

*Edit

oops, I forgot to mention that all my tubing is 1/2" ID

Just to help...

Copper pipe is very hard to bend.
3/4" is actually 7/8" OD, 1/2" pipe is 5/8" OD actual etc...
Soldered fittings is the way to go to get elbows and bends.

Copper tubing (aka refrigerator tubing) is a thin walled version.
It can be bent by hand without too much trouble. You can fill it with salt or sand to help keep it from kinking while bending.
There are spring sets made to slip over the tubing that also help to keep it from colapsing, and these are relatively cheep. I got mine at Menards for $7 with 5 different sizes.
Tubing sizes are actual OD sizes, meaning that 1/2" tubing is really 1/2" OD.
Since the OD is the same size as plastic tubing's ID, the fit isn't that tight. I use brass compression sleeves (ferules) soldered on the end to make a kind of barb, then I can use any type of clamp/ziptie I like without having to resort to worm-drive clamps (teh ugly).
You can also use pipe elbows on the soft tubing, but use the correct sizes...3/8 pipe fittings exactly fit 1/2" tubing etc...

That help?

*Oh, one more thing, don't expect to get those nice tight 1" radius bends that you see used on some A/C radiators and such. Those are machine bent using much power, heat, and mandrells.

The soft copper isn't really thinner walled than rigid copper (unless you're getting into type-K & such)...sorta weird. Anyways, rigid copper (pipe) is commonly measured by its ID (nominal size), and soft copper (tube) measure by it's OD. The typical wall size for copper tubing is 1/16", but higher grade rigid pipe will be a tad more.

As for the bends, copper elbows are of the sweeping sort, rather than the less-desirable mitre elbows (drilled not formed; machined brass, plastic). If you can solder them (easy, just practice), its not a problem. As for bending the soft copper, its easy as long as you don't do bends within 4 inches or so of an end, and getting the tube reeeally hot helps too.