Sample size for a one sample t-test
This spreadsheet computes the total sample size for a one sample t-test with given power.
This can also be done using this on-line calculator. Both these programs use the more liberal normal quantiles as opposed to t quantiles for sample size evaluation.
The web calculator here uses the formula on page 39 of
Kraemer HC and Thiemann S (1987) How many subjects? Statistical power analysis in research. Sage.:London. (There should be a copy of this book in the CBU library).
The formula is: N for paired t-test = (1.96+0.842)^2 x (difference in paired means / sd of the DIFFERENCE in the means) for 80% power, two-tailed type I error of 5%.