Higgs pair production provides a unique handle for measuring the strength of the Higgs self interaction and constraining the shape of the Higgs potential. Among the proposed future facilities, a circular 100 TeV proton-proton collider would provide the most precise measurement of this crucial quantity. In this work, we perform a detailed analysis of the most promising decay channels and derive the expected sensitivity of their combination, assuming an integrated luminosity of 30 ab$^{-1}$. Depending on the assumed systematic uncertainties, we observe that the Higgs self-coupling will be measured with a precision in the range 3.4 - 7.8% at 68% confidence level.