This paper presents the high-pressure equation of state (EOS) for NaCl, KCl, and CsCl, calculated using a Mie-Grüneisen approach with improved compressibility values. The calculation was extended to KCl and CsCl, and the results were compared with experimental data. The study shows that the theoretical approach provides pressures with accuracy comparable to experimental measurements above 25 kbar, making it a practical pressure scale. The EOS calculations for NaCl, KCl, and CsCl were based on the Mie-Grüneisen equation, with parameters adjusted to match experimental data for thermal expansion and bulk modulus. The Grüneisen parameter was modeled as a function of volume, and the calculation included contributions from nearest-neighbor repulsion, second-nearest-neighbor repulsion, thermal vibration, Coulomb attraction, and Van der Waals attraction. The results showed good agreement with experimental measurements for NaCl and CsCl, with the calculated pressures matching well with shock measurements and Bridgman compression data. The calculated cohesive energies for NaCl, KCl, and CsCl were found to be in excellent agreement with experimental values, indicating that the electron affinity is accurately predicted by the theory. However, the theory's accuracy is limited by uncertainties in input parameters, with an estimated error of up to 2.4% below 200 kbar. The study also highlights the importance of a good approximation to the interatomic potential for accurate P-V-T measurements. The results demonstrate that the Mie-Grüneisen approach provides a reliable EOS for alkali halides, with the calculated pressures showing good agreement with experimental data. The study also notes that the theory is not accurate for higher-order derivatives of thermodynamic variables, but it remains a useful tool for pressure calibration. The paper concludes that the theory is accurate enough for current experimental capabilities and can be used as a practical pressure scale until more precise measurements are available.This paper presents the high-pressure equation of state (EOS) for NaCl, KCl, and CsCl, calculated using a Mie-Grüneisen approach with improved compressibility values. The calculation was extended to KCl and CsCl, and the results were compared with experimental data. The study shows that the theoretical approach provides pressures with accuracy comparable to experimental measurements above 25 kbar, making it a practical pressure scale. The EOS calculations for NaCl, KCl, and CsCl were based on the Mie-Grüneisen equation, with parameters adjusted to match experimental data for thermal expansion and bulk modulus. The Grüneisen parameter was modeled as a function of volume, and the calculation included contributions from nearest-neighbor repulsion, second-nearest-neighbor repulsion, thermal vibration, Coulomb attraction, and Van der Waals attraction. The results showed good agreement with experimental measurements for NaCl and CsCl, with the calculated pressures matching well with shock measurements and Bridgman compression data. The calculated cohesive energies for NaCl, KCl, and CsCl were found to be in excellent agreement with experimental values, indicating that the electron affinity is accurately predicted by the theory. However, the theory's accuracy is limited by uncertainties in input parameters, with an estimated error of up to 2.4% below 200 kbar. The study also highlights the importance of a good approximation to the interatomic potential for accurate P-V-T measurements. The results demonstrate that the Mie-Grüneisen approach provides a reliable EOS for alkali halides, with the calculated pressures showing good agreement with experimental data. The study also notes that the theory is not accurate for higher-order derivatives of thermodynamic variables, but it remains a useful tool for pressure calibration. The paper concludes that the theory is accurate enough for current experimental capabilities and can be used as a practical pressure scale until more precise measurements are available.