Use this race prediction calculator to set realistic running goals. As with any prediction tool, it is not an exact science but it should give you a good idea for the approximate time to aim for.
There are many race prediction formulas out there, but please do not limit or over-extend your capabilities based on this. You'll often see a predict-your-time 5k race prior to many marathons, as this has proven to be a reliable indicator for many distance runners.
If you haven't run any of the three race distances listed under 'Base Distances', go to the track and do a self time-trial. Remember that one lap around the track is 400 meters. I find that tools like this come in handy when attempting to set race pace goals. For example, I’ve often had my sights on breaking a 3-hour marathon and know that I’ve lacked the speed to do this. By playing with the calculator a bit, I’ve deduced that I’ll need to break 38 minutes in a 10k (or break 18 minutes in a 5k) to be at the desired fitness level to break 3 hours in a marathon. Bottom line: The calculator helps me set realistic race goals.
Goals that are too easy or too hard can deflate our ego and detract from our momentum. So now that you have a realistic target, set your goal and pursue it to the best of your ability.