In this work the lattice deformation induced by substitutional B in Si is carefully determined by using different experimental techniques. The investigated Si1−xBx∕Si layers x=(0.0012÷0.005) are grown by solid phase epitaxy of B-implanted preamorphized Si and by molecular beam epitaxy. Nuclear reaction analysis both in random and in channeling geometry, secondary ion mass spectrometry and high resolution x-ray diffraction allow to quantify the total amount of B and its lattice location, the B depth profile and the B-doped Si lattice parameter, respectively. The reasons for the large spread present in the data reported so far in literature are discussed. Our results, thanks to the synergy of the earlier techniques, lead to a significantly more accurate strain determination, that is in agreement with very recent ab initio theoretical calculations.