A method for autonomously determining at least one trim of a motor vehicle, said trim ( α) illustrating the angle between a longitudinal frame reference axis of the motor vehicle and a longitudinal axle reference axis of the motor vehicle, comprising: - a measurement step implemented using at least two accelerometers (A1, A2) linked to the frame of the vehicle, the two accelerometers (A1, A2) being configured to measure, respectively, an acceleration referred to as longitudinal and an acceleration referred to as vertical of the motor vehicle, the measurement step consisting in measuring a plurality of successive measurement sets, each measurement set comprising at least one measured longitudinal acceleration and one measured vertical acceleration; and - a calculation step implemented for a calculation unit and consisting of calculating the trim ( α) of the vehicle using exclusively the measurements made in the measurement step, said calculation step considering that the vertical acceleration (Az) and the longitudinal acceleration (Ax) are linked together by an affine function via a proportionality coefficient a1 depending on the trim ( α) for a constant road slope, said calculation step comprising: • a first sub-step consisting of implementing a linear regression, using a plurality of measurement sets each comprising at least a vertical acceleration (Az) and a longitudinal acceleration (Ax), in order to determine a proportionality coefficient a1, said first sub-step being implemented a plurality of times to obtain a plurality of proportionality coefficients a1; and • a second sub-step consisting of determining said trim (α), from the proportionality coefficients a1 determined in the first sub-step; the method being characterised in that: the measurement step consists of also measuring, using a third accelerometer, a lateral acceleration which is orthogonal to said vertical and longitudinal accelerations, said lateral acceleration measured in the measurement step being used in the calculation step at least to eliminate non-rectilinear trajectories within predetermined margins, said proportionality coefficient a1 satisfying the following relationship: a 1 = a 0 + Kzx wherein: • Kzx is an internal parameter of the system; and • a0 = -tgα, α being the trim and tg the tangent, and the calculation step comprising an auxiliary sub-step consisting of calculating the internal parameter of the system Kzx. - a measurement step implemented using at least two accelerometers (A1, A2) linked to the frame of the vehicle, the two accelerometers (A1, A2) being configured to measure, respectively, an acceleration referred to as longitudinal and an acceleration referred to as vertical of the motor vehicle, the measurement step consisting in measuring a plurality of successive measurement sets, each measurement set comprising at least one measured longitudinal acceleration and one measured vertical acceleration; and - a calculation step implemented for a calculation unit and consisting of calculating the trim ( α) of the vehicle using exclusively the measurements made in the measurement step, said calculation step considering that the vertical acceleration (Az) and the longitudinal acceleration (Ax) are linked together by an affine function via a proportionality coefficient a1 depending on the trim ( α) for a constant road slope, said calculation step comprising: • a first sub-step consisting of implementing a linear regression, using a plurality of measurement sets each comprising at least a vertical acceleration (Az) and a longitudinal acceleration (Ax), in order to determine a proportionality coefficient a1, said first sub-step being implemented a plurality of times to obtain a plurality of proportionality coefficients a1; and • a second sub-step consisting of determining said trim (α), from the proportionality coefficients a1 determined in the first sub-step; • a first sub-step consisting of implementing a linear regression, using a plurality of measurement sets each comprising at least a vertical acceleration (Az) and a longitudinal acceleration (Ax), in order to determine a proportionality coefficient a1, said first sub-step being implemented a plurality of times to obtain a plurality of proportionality coefficients a1; and • a second sub-step consisting of determining said trim (α), from the proportionality coefficients a1 determined in the first sub-step; the measurement step consists of also measuring, using a third accelerometer, a lateral acceleration which is orthogonal to said vertical and longitudinal accelerations, said lateral acceleration measured in the measurement step being used in the calculation step at least to eliminate non-rectilinear trajectories within predetermined margins, said proportionality coefficient a1 satisfying the following relationship: a 1 = a 0 + Kzx wherein: • Kzx is an internal parameter of the system; and • a0 = -tgα, α being the trim and tg the tangent, • Kzx is an internal parameter of the system; and • a0 = -tgα, α being the trim and tg the tangent, and the calculation step comprising an auxiliary sub-step consisting of calculating the internal parameter of the system Kzx.