Analysing techniques such as (μ)PIXE (mu particle induced X-ray emission) and (μ)RBS (mu Rutherford or nuclear backscattering spectroscopy) now are widely used for the quantitative determination of the concentration of elements in a variety of samples. Proton beams with energies around 3 MeV are preferably used for this purpose. For the calculation of the concentration it is necessary that the energy of the proton beam be well known. In this paper we present three nuclear calibration methods for use with cyclotrons: a resonant reaction, a combination of elastic and inelastic scattering and a (p, α) reaction. The energy of the Eindhoven cyclotron proton beam around 3 MeV has been determined to be (62 ±18) keV lower than the nominal value.