# Cooling Load Calculator

> Calculate cooling load step by step: Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W).

Page: https://freecalculator.tech/tools/cooling-load-calculator
Last reviewed: 2026-11-03

## Formula

Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W).

- 0.33 W·h/m³·K is the volumetric heat capacity of air (ρ·cp ≈ 1.2 × 1,005 ÷ 3,600).
- Sensible load only — solar gain through glass and latent (humidity) load are not included unless you add them to internal gains.
- This is a simplified estimate, not a full ASHRAE or Manual J calculation.
- Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W).
- Inputs used: Envelope U × A (sum over walls, roof, windows), Design indoor–outdoor temperature difference, Room volume, Air changes per hour, Internal gains (people, lights, equipment).

## Inputs

- Envelope U × A (sum over walls, roof, windows)
- Design indoor–outdoor temperature difference
- Room volume
- Air changes per hour
- Internal gains (people, lights, equipment)

## Sensible cooling load formula

Q = fabric gain + ventilation gain + internal gains. Fabric = sum of U x A x temperature difference. Ventilation = 0.33 x air changes per hour x room volume x temperature difference, in watts.

## What this estimate leaves out

Solar gain through glazing and latent load from humidity are not included. In sunny or humid rooms both can be large, so treat the result as an early estimate and not an equipment selection.

## Converting watts to BTU/h and tons

BTU/h = watts x 3.412. One ton of refrigeration is 12,000 BTU/h, about 3.517 kW.

## Worked example: small office

1. Fabric = 80 W/K x 8 K = 640 W
2. Ventilation = 0.33 x 1 x 120 x 8 = 316.8 W
3. Total = 640 + 316.8 + 600 = 1,556.8 W, about 5,312 BTU/h

## Common questions

### Why doesn't this include sun through windows?

Solar gain depends on orientation, shading and glazing and needs hourly methods. Add an estimate to internal gains if you have one.

### What about humidity?

Latent load from moisture is separate and can be significant in humid climates. This tool calculates sensible load only.

### Can I size equipment from this?

Use it for early estimates. Equipment sizing should follow a full load calculation by a qualified designer.

### How do I use the Cooling Load Calculator?

Enter the required values for Envelope U × A (sum over walls, roof, windows), Design indoor–outdoor temperature difference, Room volume, Air changes per hour, Internal gains (people, lights, equipment). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.

### What formula does the Cooling Load Calculator use?

Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W). The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.

### Can the Cooling Load Calculator be used for exact decisions?

Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.

## Limitations and assumptions

- Sensible load only.
- No solar or thermal mass effects.
- Not a substitute for Manual J / ASHRAE load calculations.
- Results are estimates for planning and learning. Real designs, installations and bids must be checked by a qualified, licensed professional against the codes that apply where you work.
- The result depends on the values you enter for this cooling load calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.

## Sources

- ASHRAE — https://www.ashrae.org/technical-resources/ashrae-handbook

## Cite this page

- APA: Free Calculator. (2026, November 3). Cooling Load Calculator. https://freecalculator.tech/tools/cooling-load-calculator
- MLA: "Cooling Load Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/cooling-load-calculator.
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