Equilateral triangle with three sets of grid lines: the standard format for plotting three-component compositions in chemistry, metallurgy and soil science.

Free printable ternary plot paper PDF. Equilateral triangle with three sets of 10% gridlines for plotting three-component compositions.

Ternary Plot Paper | Free Printable PDF

Ternary Plot Paper

To read the percentage of component A at a point, find the gridline that runs parallel to the side opposite vertex A and passes through your point. The percentage of A is given by where that gridline meets the A-axis edge. The same trick works for B and C. The three percentages always sum to 100%.

Read percentages along the parallel gridlines

Soil scientists put clay at the top vertex, sand at the bottom-right, silt at the bottom-left. Metallurgists vary by alloy system. Pick the convention used in your discipline's textbooks; consistency matters more than which assignment is 'right'.

Choose vertex order to match convention in your field

For phase diagrams, plot the key compositions (eutectics, peritectics, pure-phase boundaries) as labelled dots before drawing any curves through them. Curves drawn through dots look intentional; curves drawn freehand sometimes drift through compositions that don't exist in the real system.

Mark compositions before plotting curves

If you fix one component and vary the others, you get a ternary plot in three remaining components. Stacking several such plots (each at a different fixed value of the fourth) is a common way to visualise four-component systems where a 3D representation would be illegible.