According to relative ASTM or ASME standards, there are four grades of unalloyed titanium (commercially pure titanium): grade 1, grade 2, grade 3, and grade 4. They are designated with UNS number R50250 (Gr.1), R50400 (Gr.2), R50550 (Gr.3), and R50700 (Gr.4), respectively.

Grade	C	O	N	H	Fe	O.E.E	O.E.T
1	≤0.08	≤0.18	≤0.03	≤0.015	≤0.20	≤0.1	≤0.4
2	≤0.08	≤0.25	≤0.03	≤0.015	≤0.30	≤0.1	≤0.4
3	≤0.08	≤0.35	≤0.05	≤0.015	≤0.30	≤0.1	≤0.4
4	≤0.08	≤0.40	≤0.05	≤0.015	≤0.50	≤0.1	≤0.4

*O.E.E: other elements, each; O.E.T: other elements, total; all values are in weight %.

These unalloyed titanium grades contain varying amounts of impurities such as carbon, oxygen, nitrogen, hydrogen and iron, etc (see chemical composition requirements in the above table). It is very difficult and inconvenient to distinguish between the various grades of unalloyed titanium on the basis of chemical analysis since they have very close impurity content of each element. However, the impurity atoms will occupy interstitial sites by diffusion. Even a small amount of interstitial impurities can greatly affect the mechanical properties of pure titanium. Thus, unalloyed titanium mill products are more readily distinguished by mechanical properties (see the table below).

Grade	Tensile Strength ksi [MPa]	Yield Strength ksi [MPa]	Elongation, in 2", %
1	≥35 [240]	20 [138] ~ 45 [310]	≥24
2	≥50 [345]	40 [275] ~ 65 [450]	≥20
3	≥65 [450]	55 [380] ~ 80 [550]	≥18
4	≥80 [550]	70 [483] ~ 95 [655]	≥15

*Mechanical properties in accordance with ASME SB-265/ ASTM B265, annealed titanium plates.