The paper analyses the pricing of various types of thermal coal on the international market in the period 2015–2025. Coal prices during this period fluctuated significantly under the influence of factors, such as: demand, supply, production costs and global events, e.g., the COVID-19 crisis, Russia’s aggression against Ukraine and climate policies. The major benchmark is the price of Australian coal 6,000 kcal/kg (25 MJ/kg) quoted at the port of Newcastle (NEWC), which reflects market trends. During the period under analysis, prices went through three phases: stable, dynamic growth (2021–2022) and stabilization after the peak. The analysis covered the pricing of types with different calorific values, from 6,000 to 3,400 kcal/kg, and examined how changes in calorific value affect pricing. It was calculated that a decrease in calorific value by 1 MJ/kg causes a price change of approximately 6–7% (relative to the base price of coal: 6,000 kcal/kg), although in periods of high volatility this indicator was as high as 8–10%. The results confirm the stability of valuation methods over different periods, and indicate that the valuation of coal types with lower calorific value is proportional to the decrease in the energy content of coal. In summary, despite high price volatility, the relationship between the valuation of different quality coals is largely stable and based on energy parameters, which allows for a rational estimation of their value on the international market. A pricing formula has been proposed to calculate the prices of different coal types using the calculated price gradation coefficient.