Theory

In 5GNR the ideal throughput formula is obtained by multiplying the following
1. Modulation bits / symbol (8 for 256QAM, 6 for 64QAM) ,
2. Scaling Factor (from 0 to 1) In this calculator you can use it to introduce the DL/UL factor based on slot format as well as BLER of the scheduler to get a closer to practical limit ,
3. Max Coding Rate (from 3GPP MCS Index table) (948/1024 is the max) ,
4. Assigned PRBs (upto 273 for 30Khz on 100MHz bandwidth) ,
5. ( 12 / 10e-3 / (14 * 2^numerology)) which is basically the calculation for Sampling Time (Ts) ,
6. (1 - Overheads) where overheads are defined for each Frequency range and DL/UL direction ,
7. Number of layers which can be upto 8 for DL and 4 for UL on device level

An example can be seen in the 5G Cheat sheet as well (browse on the menu and select cheatsheet)