Users who are interested in approximate data rate values can use the formula 

Data Rate = BW * Q * R * N * (1 - OH)

where BW is the bandwidth, Q is the modulation order, R is the code rate, N is the number of MIMO layers and Overhead (OH) can be broadly approximated as 1/7. in TDD, this is the two-way (DL + UL) data rate. Therefore the DL alone data rate would be

DL-rate = Data-rate * DLratio

While BW, OH, and N are fixed by input, Q and R are dependent on the MCS chosen. The transmitter adapts its PHY layer Modulation and coding (MCS) depending on the receiver's SNR. The SNR in turn depends on the received power. And, received-power is transmit-power less pathloss.  

In NetSim users can use the radio measurements workspace to obtain the SINR - and MCS, Modulation scheme (which determines the modulation order), and coding rate - for each UE over time.

Example: Let us say we have a case where

BW = 40 MHz

MCS = 13 which means modulation is 64 QAM (Q = 6) and R = 567/1024

DL/UL ratio = 4:1 which implies DL ratio = 4/5

Transmit antennas = receive antennas = 1, and therefore number of MIMO layers = 1

The data rate would then be

40 * 6 (64 QAM) * (567/1024) (Code rate) * 1 * 4 / 5 (UL Ratio) * (1 - 1/7) (Overheads) = 91.125 Mbps

Exact formula

The 5G data rate (PHY bit rate) in NetSim is given by

Date Rate = N * Q * R * f * (Nprb * 12 / Ts) * (1 - OH)

where N is the number of layers, Q is the modulation order, R is the code rate, f is a scaling factor, Nprb is the maximum Resource Block allocation, Ts is the symbol duration and OH is the overhead. Complete details of this are provided in NetSim's 5G user manual.

Useful websites

Overview of NetSim 5G library