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Trades & Professional Tools · HVAC

Wet Bulb Temperature Calculator

Estimate near-surface psychrometric wet-bulb temperature from dry bulb and RH with the pressure-independent Stull empirical approximation.

Trades & Professional Tools · HVAC

Enter your project measurements

Measured inputs · visitor-entered product and design assumptions

Use one consistent unit basis and measurements taken at the stated locations and operating condition. Enter project, manufacturer, fluid-property, pressure-temperature, efficiency, and test criteria from the actual system. Values stay in this browser.

Trade calculator result

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Enter valid values to see the result.

Your entries are calculated in this browser and are not submitted to 365CALCS.COM.

Quick guide

How to use this calculator

  1. Choose the calculation mode or measurement system that matches the values you actually have.
  2. Enter measured project dimensions and use product-specific coverage, density, yield, resistance, or waste data where requested.
  3. Review the intermediate results before ordering material or applying the result on site.

Calculation method

Calculation method

Tw≈T atan[0.151977(RH+8.313659)^0.5]+atan(T+RH)−atan(RH−1.676331)+0.00391838 RH^1.5 atan(0.023101RH)−4.686035; no pressure correction is modeled.

The calculator preserves full internal precision and rounds only displayed results. Quantity outputs round up when whole purchasable pieces are required.

Worked example

Worked example

30°C and 50% RH gives about 22.3°C.

Tw≈T atan[0.151977(RH+8.313659)^0.5]+atan(T+RH)−atan(RH−1.676331)+0.00391838 RH^1.5 atan(0.023101RH)−4.686035; no pressure correction is modeled.

Supported inputs

Precision and limits

HVAC design and service boundary

HVAC results use the measured, design, manufacturer, psychrometric, fluid-property, pressure-temperature, efficiency, and test values you enter. They do not perform or certify Manual J, D, or S procedures; supply ventilation or code defaults; select equipment; identify refrigerant; determine a safe charge; authorize combustion, pressure, electrical, or refrigerant work; or replace approved manufacturer data and a qualified HVAC professional.

Planning scope

This calculator supports measurement, estimating, and scenario planning. It does not inspect a site, select a product, certify a design, or replace drawings, specifications, manufacturer instructions, local codes, permits, or a qualified trade professional.

Measured and product-specific inputs

Nominal dimensions can differ from actual dimensions. Verify inside pipe diameters, actual lumber sizes, product coverage, bag yield, material density, conductor resistance, waste, and packaging against the materials used on the project.

Safety and regulatory limits

Electrical, HVAC, structural, excavation, roofing, pressure, lifting, and life-safety work may require jurisdiction-specific calculations and professional approval. Do not use a generic planning result as a code-compliance or safety determination.

Precision and privacy

Inputs accept bounded plain decimals. Calculations remain in this browser and raw entered project values are not submitted to 365CALCS.COM.

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