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Sap flow probes are routinely used in forest and horticulture hydrology for estimating tree water use. This requires unbiased measurements when upscaling from tree to stand level, but accuracy and comparability of different thermometric methods have been questioned. Three sap flow measuring techniques were compared against gravimetric flow measurement in cut stem segments: ‘Granier-type’ thermal dissipation probes (TDP; three different sensor types), the heat field deformation method (HFD), and the heat ratio method (HRM). For the empirical methods (TDP and HFD), new calibration parameters were estimated using a nonlinear hierarchical modelling approach. 66 stem segments from five temperate, diffuse-porous tree species (9–16 cm stem diameter, 100 cm stem length) were exposed to a wide range of flux densities by applying subatmospheric pressure (−50 to −650 hPa) analogous to natural flow …