def min_max(box, width):
    """Get box width from given width and box min- and max-widths."""
    min_width = box.style['min_width']
    max_width = box.style['max_width']
    if min_width == 'auto' or min_width.unit == '%':
        min_width = 0
    else:
        min_width = min_width.value
    if max_width == 'auto' or max_width.unit == '%':
        max_width = float('inf')
    else:
        max_width = max_width.value
    return max(min_width, min(width, max_width))
