You can use your calculator.

If you have an 83, 83+, 84, or 84+ you can do this pretty easily...

From the home screen go to the distribution menu. [2nd] [VARS]

Highlighted right away is [1] normalcdf(

Hit [ENTER].

Now you should see normalcdf( on your screen

Since you don't have an infinity button (like the 89), type in a really large negative number (use -1 E 9) where E is retrieved by hitting [2nd] [,].

Hit [,].

Now enter your z value.

Then hit [ENTER]

Let's say my z value was 5.3

Then my percentage would be normalcdf(-1E9,5.3)$\displaystyle \approx 0.999999942$.

Rounding to 2 decimal places, this would give us 100% or 1.

As z gets larger and larger, we assume that the percentage is 100% or 1.

Hope this makes sense.