critical t values

If there are 50 observations and we want the critical t-value for a 95% confidence level (1 independent variable), how would we get the critical t?

50-k-1 = 48 degrees of freedom so i looked in the t-table and obviously we only have values for 40 and 60 df…do we just do a linear interpolation between the two to get to a t-value for 48df?