An image forming system includes an image forming apparatus including a housing where an image forming unit is provided and a strain detector, a hardware processor, and a storage. The strain detector detects strain of a bottom plate of the housing. The processor and the storage are included in or provided outside the image forming apparatus. The processor obtains a first detection signal from the detector, stores strain measured data based on the first detection signal as reference data in the storage, obtains a second detection signal from the detector after storing the reference data, compares strain measured data based on the second detection signal with the reference data, and determines whether adjustment of a supporting point height of the bottom plate to reduce the strain due to change over time from a time of the obtainment of the reference data is required.