Student's T-Test Table

Here we have "Critical T Values" for Student's T-Test for different confidence levels and degrees of freedom (df):

How to use this table:

  1. Choose if you are doing a one-tail or two-tail test
  2. Find the column for your alpha level (like 0.05)
  3. Find the row for your degrees of freedom (df)
  4. The number where they meet is your Critical T Value!
1-tail 0.2 0.1 0.05 0.025 0.02 0.01 0.005 0.0025 0.002 0.001
2-tail 0.4 0.2 0.1 0.05 0.04 0.02 0.01 0.005 0.004 0.002
df 1 1.376 3.078 6.314 12.71 15.89 31.82 63.66 127.3 159.1 318.3
2 1.061 1.886 2.920 4.303 4.849 6.965 9.925 14.09 15.76 22.33
3 0.978 1.638 2.353 3.182 3.482 4.541 5.841 7.453 8.053 10.21
4 0.941 1.533 2.132 2.776 2.999 3.747 4.604 5.598 5.951 7.173
5 0.920 1.476 2.015 2.571 2.757 3.365 4.032 4.773 5.030 5.893
6 0.906 1.440 1.943 2.447 2.612 3.143 3.707 4.317 4.524 5.208
7 0.896 1.415 1.895 2.365 2.517 2.998 3.499 4.029 4.207 4.785
8 0.889 1.397 1.860 2.306 2.449 2.896 3.355 3.833 3.991 4.501
9 0.883 1.383 1.833 2.262 2.398 2.821 3.250 3.690 3.834 4.297
10 0.879 1.372 1.812 2.228 2.359 2.764 3.169 3.581 3.716 4.144
11 0.876 1.363 1.796 2.201 2.328 2.718 3.106 3.497 3.624 4.025
12 0.873 1.356 1.782 2.179 2.303 2.681 3.055 3.428 3.550 3.930
13 0.870 1.350 1.771 2.160 2.282 2.650 3.012 3.372 3.489 3.852
14 0.868 1.345 1.761 2.145 2.264 2.624 2.977 3.326 3.438 3.787
15 0.866 1.341 1.753 2.131 2.249 2.602 2.947 3.286 3.395 3.733
16 0.865 1.337 1.746 2.120 2.235 2.583 2.921 3.252 3.358 3.686
17 0.863 1.333 1.740 2.110 2.224 2.567 2.898 3.222 3.326 3.646
18 0.862 1.330 1.734 2.101 2.214 2.552 2.878 3.197 3.298 3.610
19 0.861 1.328 1.729 2.093 2.205 2.539 2.861 3.174 3.273 3.579
20 0.860 1.325 1.725 2.086 2.197 2.528 2.845 3.153 3.251 3.552
21 0.859 1.323 1.721 2.080 2.189 2.518 2.831 3.135 3.231 3.527
22 0.858 1.321 1.717 2.074 2.183 2.508 2.819 3.119 3.214 3.505
23 0.858 1.319 1.714 2.069 2.177 2.500 2.807 3.104 3.198 3.485
24 0.857 1.318 1.711 2.064 2.172 2.492 2.797 3.091 3.183 3.467
25 0.856 1.316 1.708 2.060 2.167 2.485 2.787 3.078 3.170 3.450
26 0.856 1.315 1.706 2.056 2.162 2.479 2.779 3.067 3.158 3.435
27 0.855 1.314 1.703 2.052 2.158 2.473 2.771 3.057 3.146 3.421
28 0.855 1.313 1.701 2.048 2.154 2.467 2.763 3.047 3.136 3.408
29 0.854 1.311 1.699 2.045 2.150 2.462 2.756 3.038 3.127 3.396
30 0.854 1.310 1.697 2.042 2.147 2.457 2.750 3.030 3.118 3.385
40 0.851 1.303 1.684 2.021 2.123 2.423 2.704 2.971 3.054 3.307
50 0.849 1.299 1.676 2.009 2.109 2.403 2.678 2.937 3.018 3.261
60 0.848 1.296 1.671 2.000 2.099 2.390 2.660 2.915 2.994 3.232
70 0.847 1.294 1.667 1.994 2.093 2.381 2.648 2.899 2.977 3.211
80 0.846 1.292 1.664 1.990 2.088 2.374 2.639 2.887 2.964 3.195
90 0.846 1.291 1.662 1.987 2.084 2.368 2.632 2.878 2.954 3.183
100 0.845 1.290 1.660 1.984 2.081 2.364 2.626 2.871 2.946 3.174
1000 0.842 1.282 1.646 1.962 2.056 2.330 2.581 2.813 2.885 3.098
10000 0.842 1.282 1.645 1.960 2.054 2.327 2.576 2.808 2.879 3.091

When our degrees of freedom are very high (like over 1000), the T-distribution looks almost exactly like the Standard Normal Distribution.

Notice that the two-tail alpha is always double the one-tail alpha for the same column. This is because a two-tail test splits the probability into two equal parts at both ends of the curve!
Student's T-Test Data Index