Psychrometric Calculator

Dry/wet bulb temperature, relative humidity, dew point, enthalpy and specific volume calculations. Essential tool for HVAC engineers.

What is the Psychrometric Calculator?

The psychrometric calculator is an engineering tool used to determine the thermodynamic properties of moist air. It calculates psychrometric quantities including dry-bulb temperature, wet-bulb temperature, relative humidity, dew point, absolute humidity, enthalpy, and specific volume.

Calculations are based on ASHRAE Fundamentals 2021 standards. Hyland-Wexler polynomials are used for saturation vapor pressure; the ice surface equation applies below 0°C, and the water surface equation above 0°C. Error stays under 0.01% across the HVAC design band (−40°C to +60°C) and under 0.05% in extreme conditions (down to −60°C for lithium-ion dry rooms; up to +100°C for industrial hot process air). The +100°C upper bound is the classical psychrometric limit at 1 atm — the boiling point of water.

The tool accepts any two psychrometric variables as input and automatically calculates all remaining properties. When the dew point is negative, the frost point is also displayed separately. Altitude correction ensures accurate results at different elevations.

The calculated point is visually plotted on the psychrometric chart. This feature is important for visualizing air conditioning processes in HVAC system design.

Applications

• HVAC system design
• Industrial humidity control
• Pharmaceutical and clean room engineering
• Food storage and cold chain
• Lithium battery production dry rooms
• Textile and printing

Articles related to this calculator

In-depth content to support your engineering decision after completing the calculation.

Reference Guide

Why Relative Humidity, Absolute Humidity and Dew Point Matter in Humidification

RH, absolute humidity and dew point measure water in the air from three different perspectives. Correct parameter selection drives humidifier sizing, sensor architecture and control algorithm.

Read article

Technical Article

How to Read a Psychrometric Chart for Humidification Systems

A practical reading guide to interpret the psychrometric chart on the field: axes, locating an air state, how humidification processes look on the chart, and reading capacity off the chart.

Read article

Technical Article

Relative Humidity Measurement: Common Errors and How to Avoid Them

Relative humidity measurements play a critical role in many areas, from manufacturing facilities to laboratory environments, from warehouses to HVAC systems.

Read article

Technical terms used in this tool

Access concise ASHRAE-referenced definitions of technical concepts you encounter in the calculation.

Frequently Asked Questions

Other Tools