Is anyone using a fixed R for stop placement?

Been trying to get a handle on my position sizing and saw some guys talking about a fixed R (risk unit) for stop loss placement, rather than a fixed percentage of capital or just an arbitrary point. The idea is you define your maximum acceptable loss per trade, say 1% of your account, and then your stop is always set so that if hit, it equals that 1%. This means your share size changes constantly depending on volatility. Is anyone actually doing this in practice, and how are you handling the constant calculation?