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t Distribution CalculatorStatLens

Left Right Between Symmetric

t value Upper t Probability

Degrees of freedom

t Distribution Calculator

Computes areas (probabilities) under a t curve. The t distribution is bell-shaped like the normal but has heavier tails; its exact shape depends on the degrees of freedom.

Region to shade

The buttons above the chart choose which area is shaded and reported:

Left — area below the boundary
Right — area above the boundary
Between — area in the middle band between two boundaries (a second input appears)
Symmetric — the two outer tails, mirrored about 0 (useful for two-sided critical values)

Two-way lookup

The calculator works in both directions — edit whichever value you know:

Type a boundary in the t value box to get the shaded area.
Type an area in the Probability box to get the t value (the critical value) that produces it.

You can also drag the boundary line(s) directly on the chart. The banner beside the buttons reports the current area.

Degrees of freedom

Set Degrees of freedom with the number box or the slider. Fewer df means heavier tails; as df grows the curve approaches the standard normal.

Keyboard shortcuts

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