I built Running Level https://runninglevel.com/ recently along the same lines as my other site Strength Level https://strengthlevel.com/ but have only done a soft launch. Gyms are closed here in the UK so a lot of us are out running instead.

Running Level has running standards for your age/gender over many distances like 10k/marathon/mile. The calculator on the homepage helps you rate your running performance against other people your age/gender, predicts race performance and recommends some training times.

I was hoping to do a Show HN or Product Hunt but marketing has never been my strong suit. Hope someone likes it!