As a general rule of thumb, you should allow for a margin of around 25% when considering how much tow capacity you need. For example, if you were towing a 3500 lb trailer, a vehicle with a maximum towing capacity of 5000 lbs should be able to do the job without issues. This gives you enough wiggle room to handle all driving situations, including steep inclines, without putting an excessive strain on your vehicle and compromising safety.