If you are an XRD staker, you get a % of the total emissions for each epoch proportional to your % of the total stake. This is reduced somewhat if the node you’re staking to is taking a fee or if they are penalized for not participating fully in consensus for the epoch.
You can calculate your emissions as a staker as:
E x S x ( 100 - P ) x ( 100 - F )
E = This epoch’s total emissions XRD (fixed)
S = Your stake’s % of total delegated stake (for this epoch)
P = Penalty % for the node you’ve staked to (for this epoch)
F = Fee % for the node you’ve staked to (for this epoch)
So let’s say you are staking 1,000 XRD, and there are currently 1,000,000,000 XRD in total that are staked (out of the total supply of 9,600,000,000 XRD). The node you are delegating to has set their validator fee to 2%. And that node has 100% participation in consensus (which a good node certainly should achieve!). Your share of the rewards for the epoch will be:
E x 0.000001 x ( 100% ) x ( 98% ) = 0.00000098 of total E
Over the course of a year of about 300,000,000 XRD emitted, this means you would receive 294 XRD – a return of 29.4% APY on your original stake!
Note: This ignores the fact that your emissions will be automatically staked at each epoch, but since this is the case for everyone else, your % of total stake stays constant, leading to the same result, assuming that neither you nor anybody else is staking/unstaking.