Cooling Load Calculator
Calculate cooling load step by step: Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W).
In short
Formula: Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W).
Sensible cooling load
3.825 kW
- Fabric (U·A·ΔT)
- 3,000 W
- Ventilation (0.33·n·V·ΔT)
- 825 W
- Internal gains added
- 0 W
- BTU/h
- 13,051
What this calculator does
Calculate cooling load step by step: Q = ΣUA × ΔT + 0.33 × n × V × ΔT + internal gains (sensible load, W). Worked example, questions and limitations included.
Use it to turn Envelope U × A (sum over walls, roof, windows), Design indoor–outdoor temperature difference, Room volume, Air changes per hour, and the other shown inputs into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this thermal & hvac calculation.
Inputs and what they mean
- Envelope U × A (sum over walls, roof, windows)
- — Sum of U-value × area for each surface.
- Design indoor–outdoor temperature difference
- — number value.
- Room volume
- — number value.
- Air changes per hour
- — number value.
- Internal gains (people, lights, equipment)
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
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).
Worked example
Room with ΣUA 150 W/K, ΔT 10 K
- Fabric = 150 × 10 = 1,500 W.
- Ventilation = 0.33 × 0.5 × 250 × 10 = 412.5 W.
- Total = 1,500 + 412.5 + 1,000 = 2,912.5 W ≈ 2.91 kW.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
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.
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.
Related tools
Calculate heat transfer step by step: Conduction Q = k A ΔT ÷ L; convection Q = h A ΔT; overall Q = U A ΔT.
Calculate heating load step by step: Q = ΣUA × ΔT + 0.33 × n × V × ΔT − internal gains (not below zero).
Calculate energy consumption step by step: E = P_rated × load factor × hours/day × days/year.
Calculate equipment energy cost step by step: Cost = kWh × price per kWh + fixed or demand charges.