A combine bin level monitor may include a yield monitor to determine how much grain has been added to the combine tank, a container weighing system (e.g. scales on a grain cart) that measures the amount of grain unloaded from the combine tank and wirelessly transfers the amount to the combine bin level monitoring system. The system further includes a software routine in the combine bin level monitoring system that calculates and displays the bin level by adding grain accumulated by the yield monitor and subtracting grain accumulated by the container weighing system from the last known amount of grain in the combine tank. The accumulated grain is the amount accumulated since the last time the amount of grain in the combine tank was known.