item = {
    'Id': 123,
    'Names': [
        'foo',
        'bar',
        'qux',
        # 500 more names
    ]
}

from dynamo_size import calculate_bytes, calculate_kbytes

calculate_bytes(item)  # returns 2025
calculate_kbytes(item)  # return 1.9775390625 (2025 / 1024)