Method for determining hydrodynamic coefficients in submarines comprising a front hydroplane and a rear hydroplane, wherein the submarine is free-floating, wherein the method comprises the following steps: a) acceleration-free travel with an even keel at a constant depth and at a first first speed and a first first trim position, b) acceleration-free travel with an even keel at a constant depth and at the first first speed and a second first trim position, c) acceleration-free travel with an even keel at a constant depth and at a second first speed and the first first trim position, d) acceleration-free travel with an even keel at a constant depth and at the second first speed and the second first trim position, e) acceleration-free travel with an uneven keel at a constant depth and at a first second speed and a first front hydroplane position and a first trim tank filling, f) acceleration-free travel with an uneven keel at a constant depth and at the first second speed and a second front hydroplane position and the first trim tank filling, g) acceleration-free travel with an uneven keel at a constant depth and at the first second speed and the first front hydroplane position and a second trim tank filling, h) acceleration-free travel with an uneven keel at a constant depth and at the first second speed and the second front hydroplane position and the second trim tank filling, i) acceleration-free travel with an uneven keel at a constant depth and at a second second speed and the first front hydroplane position and the first trim tank filling, j) acceleration-free travel with an uneven keel at a constant depth and at the second second speed and the second front hydroplane position and the first trim tank filling, k) acceleration-free travel with an uneven keel at a constant depth and at the second second speed and the first front hydroplane position and the second trim tank filling, l) acceleration-free travel with an uneven keel at a constant depth and at the second second speed and the second front hydroplane position and the second trim tank filling, m) determination of hydrodynamic coefficients from the measuring variables determined in the preceding steps, wherein steps a) to 1) are carried out in any sequence, wherein step m) is carried out after steps a) to 1), wherein, during the acceleration-free travels, in each case the speed u of the submarine, the trim angle θ, the front hydroplane position δ s, the rear hydroplane angle δ b, the change in volume of the trim tanks ΔV TT and the change in volume of the depth control tank ΔV CT are detected as measuring variables. a) acceleration-free travel with an even keel at a constant depth and at a first first speed and a first first trim position, b) acceleration-free travel with an even keel at a constant depth and at the first first speed and a second first trim position, c) acceleration-free travel with an even keel at a constant depth and at a second first speed and the first first trim position, d) acceleration-free travel with an even keel at a constant depth and at the second first speed and the second first trim position, e) acceleration-free travel with an uneven keel at a constant depth and at a first second speed and a first front hydroplane position and a first trim tank filling, f) acceleration-free travel with an uneven keel at a constant depth and at the first second speed and a second front hydroplane position and the first trim tank filling, g) acceleration-free travel with an uneven keel at a constant depth and at the first second speed and the first front hydroplane position and a second trim tank filling, h) acceleration-free travel with an uneven keel at a constant depth and at the first second speed and the second front hydroplane position and the second trim tank filling, i) acceleration-free travel with an uneven keel at a constant depth and at a second second speed and the first front hydroplane position and the first trim tank filling, j) acceleration-free travel with an uneven keel at a constant depth and at the second second speed and the second front hydroplane position and the first trim tank filling, k) acceleration-free travel with an uneven keel at a constant depth and at the second second speed and the first front hydroplane position and the second trim tank filling, l) acceleration-free travel with an uneven keel at a constant depth and at the second second speed and the second front hydroplane position and the second trim tank filling, m) determination of hydrodynamic coefficients from the measuring variables determined in the preceding steps,