The environmental conditions that describe an ecosystem define the amount of energy available to the resident organisms and the amount of energy required to build biomass. Here, we quantify the amount of energy required to make biomass as a function of temperature, pressure, redox state, the sources of C, N and S, cell mass and the time that an organism requires to double or replace its biomass. Specifically, these energetics are calculated from 0 to 125°C, 0.1 to 500 MPa and −0.38 to +0.86 V using CO2, acetate or CH4 for C, NO3− or NH4+ for N and SO42− or HS− for S. The amounts of energy associated with synthesizing the biomolecules that make up a cell, which varies over 39 kJ (g cell)−1, are then used to compute energy-based yield coefficients for a vast range of environmental conditions. Taken together, environmental variables and the range of cell sizes leads to a ~4 orders of magnitude difference between the number of microbial cells that can be made from a Joule of Gibbs energy under the most (5.06 × 1011 cells J−1) and least (5.21 × 107 cells J−1) ideal conditions. When doubling/replacement time is taken into account, the range of anabolism energies can expand even further.