Generally, the Fischer–Tropsch process is operated in the temperature range of . Higher temperatures lead to faster reactions and higher conversion rates but also tend to favor methane production. For this reason, the temperature is usually maintained at the low to middle part of the range. Increasing the pressure leads to higher conversion rates and also favors the formation of long-chained alkanes, both of which are desirable. Typical pressures range from one to several tens of atmospheres. Even higher pressures would be favorable, but the benefits may not justify the additional costs of high-pressure equipment, and higher pressures can lead to catalyst deactivation via coke formation.
A variety of synthesis-gas compositions can be used. For cobalt-based catalysts the optimal H:CO ratio is around 1.8–2.1. Iron-based catalysts can tolerate lower ratios, due to the intrinsic water-gas shift reaction activity of the iron catalyst. This reactivity can be important for synthesis gas derived from coal or biomass, which tend to have relatively low H:CO ratios (< 1).