Rack Heat Load and Airflow Calculator
Convert IT power to heat load, cooling tons and the airflow needed for a given air temperature rise. With the formula, a worked example and typical values.
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Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.
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About this calculator
This page calculates heat load, cooling and airflow required from IT power in the rack and air temperature rise across the rack. Change any value or its unit and the result updates. The steps below show the working for the default values, so you can check each line against your own method.
Limits of this calculator
Real designs add margin for hot-spot mixing. Switch the airflow unit to CFM for US cooling data.
Cross-check: 8 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review.
Verification status: Indicative
Indicative. Estimation only; further engineering checks are required. Basis: Heat-load and airflow estimate.
What this calculator checks
- The arithmetic of the simplified model for the values you entered.
What remains unverified
- Whether the simplifying assumptions listed on this page hold for your case.
- Any standard, manufacturer or site data. Treat the result as an estimate and confirm it by a further engineering check.
Verification register entry
| Calculation author | Rahul Sharma (author) |
|---|---|
| Technical review | No independent technical review has been carried out |
| Individual professional approval | Not recorded |
| Formula reference | not recorded |
| Standard and edition | Not applicable: Heat load and airflow relationships are basic thermal calculations. Facility cooling design depends on equipment data and project thermal criteria; no single standard governs this calculator’s simplified equation. |
| Standard review state | Not applicable |
| Scope-screening note | not recorded |
| Cross-check test cases | 8 reference vectors (tests/reference_vectors.json) |
| Review date | not recorded |
| Next review date | not recorded |
| Status | Indicative |
Needed before this calculator can be marked Verified: reviewer name, qualification and review date; exact formula reference; formula source (textbook or standard); next review date.
Formula
Worked example
| Input | Value |
|---|---|
| IT power in the rack | 10 kW |
| Air temperature rise across the rack (K) | 12 |
- Heat = 10 kW × 3412.14 = 34,121 BTU/h
- Tons = 34,121 / 12 000 = 2.84
- V̇ = 10,000 / (1.2 × 1005 × 12) = 0.691 m³/s = 2,488 m³/h
Assumptions
- Air density 1.2 kg/m³, specific heat 1005 J/(kg·K)
- All electrical power ends up as heat in the room
- No allowance for bypass or recirculation
Real designs add margin for hot-spot mixing. Switch the airflow unit to CFM for US cooling data.
Inputs and results
| Input | Unit | Allowed or shown | Note |
|---|---|---|---|
| IT power in the rack | kW | greater than 0 kW | |
| Air temperature rise across the rack (K) | (number) | greater than 0 |
| Result | Unit | Allowed or shown | Note |
|---|---|---|---|
| Heat load (BTU/h) | (number) | Shown to 0 decimal places | |
| Cooling (US refrigeration tons) | (number) | Shown to 2 decimal places | |
| Airflow required | m³/h | Shown to 0 decimal places |
How it is calculated
Each input is converted to the base unit of its quantity, the formula above is applied in the order shown in the worked example, and each result is shown in the unit you choose. Results are held at full precision and rounded only for display, except where a step selects a standard size, as the worked example shows. A value outside its allowed range is refused with a message instead of giving a result.
How the result changes with it power in the rack
| IT power in the rack (kW) | Heat load | Cooling | Airflow required (m³/h) |
|---|---|---|---|
| 1 | 3,412 | 0.28 | 249 |
| 2.5 | 8,530 | 0.71 | 622 |
| 5 | 17,061 | 1.42 | 1,244 |
| 10 | 34,121 | 2.84 | 2,488 |
| 20 | 68,243 | 5.69 | 4,975 |
| 40 | 136,486 | 11.37 | 9,950 |
| 100 | 341,214 | 28.43 | 24,876 |
Other inputs are the same as in the worked example above.
Standards and further reading
- EN 12464-1 (lighting of indoor workplaces)
- CIE publications on photometry
Lamp and luminaire data come from the manufacturer; the illuminance targets that apply come from your project specification and local regulation. These are named as background reading. Elecmetric does not embed clause text or rating tables, and the reviewer record for this calculator is separate from this list.
Frequently asked questions
What do I need to enter?
Enter iT power in the rack and air temperature rise across the rack (K). Change the unit of a value with its selector and the result stays the same.
What does this calculator assume?
Air density 1.2 kg/m³, specific heat 1005 J/(kg·K). All electrical power ends up as heat in the room. No allowance for bypass or recirculation.
Which calculators should I use next?
Common next steps are Data Centre PUE and UPS Battery Runtime. The related links at the bottom of this page open them.
How accurate are the results?
Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. 8 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review. Check design values against the standard and the equipment data you work to.
Formula guides and reference
Longer explanations with worked examples and tables, written for the same topic.
- Cooling Formulas: Airflow and Heat Load: Cooling formulas for the airflow needed to remove heat, the temperature rise of air, watts to BTU per hour and CFM
- Fan Formulas: Air Power and Affinity Laws: Fan formulas: air power from flow and pressure, shaft power from fan efficiency, and the affinity laws for flow
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