A vehicle system includes a computer in a vehicle, and the computer includes a processor and a memory. The computer is configured to determine an operational state of a vehicle, calculate a road grade value from data from a first sensor, calculate an effective road grade value from a torque demand value, update modeling variables to map the road grade value substantially to the effective grade value when the operation state is determined to be a steady-state condition, and calculate a road grade characteristic with the road grade value and the modeling variables.