A relatively simple experimental method to estimate a diffusivity of silicon interstitials is described. In the low‐temperature range between 460 and 500 °C, oxygen thermal donors are used as a monitor for silicon interstitials. The estimated diffusivity of silicon interstitials at oxygen‐donor‐formation temperatures is fitted to previously‐published results from oxidation‐enhanced and retarded‐diffusion experiments at temperatures above 950 °C. In the temperature range between 460 and 1200 °C, the diffusivity of silicon interstitials is described by the Arrhenius equation,Di=3.35×10−1 exp(−1.86/kT) cm2/s.