Cooling Load Estimator
Estimate the peak cooling load of a room or building in kW, BTU/h and tons of refrigeration from floor area, envelope, glass, occupants, lighting, equipment and ventilation — with a sensible/latent breakdown per heat source.
Input
Space
Envelope
Opaque wall only — exclude windows.
Use 0 for an intermediate floor.
Windows
0.25 low-e glass · 0.5 clear double · 0.8 single clear.
Northern-hemisphere orientation; swap North/South in the southern hemisphere.
Internal Gains
Computers, appliances, motors — total connected heat.
Air & Conditions
Moisture content difference between outdoor and indoor air; drives latent load.
Output
| Metric | Value |
|---|---|
| No data yet | |
| Heat Source | Sensible (W) | Latent (W) | Total (W) | Share |
|---|---|---|---|---|
| No data yet | ||||
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/cooling-load-estimator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"floorArea": "30",
"ceilingHeight": "2.7",
"occupants": "4",
"wallArea": "25",
"wallU": "0.5",
"roofArea": "0",
"roofU": "0.3",
"windowArea": "5",
"windowU": "2.8",
"shgc": "0.5",
"orientation": "west",
"lighting": "10",
"equipment": "600",
"ventPerPerson": "10",
"infiltration": "0.3",
"outdoorTemp": "35",
"indoorTemp": "24",
"humidityDiff": "6",
"safetyFactor": "10"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `cooling-load-estimator` tool (Cooling Load Estimator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/cooling-load-estimator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="Cooling Load Estimator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
Also available with
Guides
What this cooling load estimator does
Sizing an air conditioner starts with the cooling load: how much heat the system must remove at the hottest hour. This tool estimates it for a room or building from floor area, walls, roof, windows, people, lighting, equipment and fresh-air ventilation. You get the result in kW, BTU/h and tons of refrigeration, plus a table showing how much each heat source contributes — so you can see whether glass, occupants or ventilation is driving the number.
How to use it
Enter the space (floor area, ceiling height, occupants), the envelope (wall and roof area with U-values), the windows (area, U-value, solar heat gain coefficient, orientation), internal gains (lighting W/m², equipment watts) and the design conditions (outdoor and indoor temperature, humidity difference, ventilation and infiltration). Results update as you type.
How it's calculated
Conduction (walls, roof, glass) = U × Area × ΔT
Window solar gain = SHGC × Area × peak solar irradiance
People = 75 W sensible + 55 W latent each
Ventilation / infiltration air = 1.23 × L/s × ΔT (sensible)
3.01 × L/s × ΔW (latent, ΔW in g/kg)
Design load = (sensible + latent) × (1 + safety margin)Walls get a +4 K sun allowance on ΔT and roofs +8 K. Lighting and equipment are treated as fully converted to sensible heat. 1 ton of refrigeration = 3,517 W = 12,000 BTU/h.
This is a screening estimate. It uses steady-state peak-hour assumptions, not a full ASHRAE heat-balance or Manual J calculation. Use it to choose a ballpark system size, and have a qualified engineer confirm before specifying equipment.
Frequently asked questions
How many tons of AC do I need? Read the "tons" line in the summary. Round up to the nearest available unit size rather than down; an undersized unit runs flat out and still struggles on the hottest days.
Why is there a latent load? Cooling air also means removing moisture. People and humid outdoor air bring water vapour that the coil must condense, which takes energy on top of lowering the temperature.
What U-value and SHGC should I use? Typical values: insulated wall 0.3–0.6 W/m²·K, roof 0.2–0.4, double glazing 2.8, low-e glass 1.6. SHGC is about 0.25 for low-e, 0.5 for clear double and 0.8 for single clear glass.
Does orientation matter? Yes. Sun-facing glass is the largest swing factor in many rooms; west glass peaks in the afternoon when outdoor air is also hottest. The orientations assume the northern hemisphere.
Privacy
Everything runs in your browser. Your building data is never uploaded or stored.