HVAC Calculators — Size, Load, Ventilation & Duct
This HVAC calculators hub gathers seven free tools for cooling tons/BTU/h, ACH→CFM ventilation, duct size, static pressure, fan laws, psychrometrics, and chiller tonnage—for workshop, warehouse, and facility planning.
Pick the step that matches your question—cooling size, ventilation, duct / ESP, or plant tons. All paths share the workflow below. For electrical feeder impact, continue to the Power Calculator hub.
Most popular: HVAC size calculator (tons / BTU/h / kW screening)—start here for load sizing, then continue to airflow and duct tools.
What are HVAC Calculators?
HVAC calculators on this hub cover the practical decision chain: first-pass cooling and heating load (tons, BTU/h, kW), ventilation airflow (CFM from ACH), duct and ESP screening, fan affinity laws, psychrometric state points, and chilled-water plant tons. Use one structured flow for workshop, warehouse, and light-commercial planning.
Common HVAC Calculations
- Estimate cooling size from floor area, ceiling height, occupancy, and climate band.
- Convert sq ft rules of thumb to tons and BTU/h for budgeting (validate with Manual J before procurement).
- Convert room volume and ACH targets to CFM for fan and duct screening.
- Screen round or rectangular duct diameter from CFM with the HVAC duct size calculator.
- Tie HVAC kW into factory load and energy cost screening on the Power hub.
Start Here
Most popular — cooling size (tons / BTU/h): Use the HVAC size calculator for load screening queries such as hvac size calculator, calculate hvac size, and hvac unit size calculator.
Need ventilation CFM? Start with ACH to CFM calculator after you know room volume and target air changes.
Need duct / trunk diameter? After CFM is known, use the HVAC duct size calculator (velocity-method screening before Manual D).
Browse all HVAC calculators · Browse planning topics · HVAC sizing authority guide
Cluster authority: HVAC sizing
For the HVAC cluster, cooling load sizing is the central knowledge entity—sensible and latent components, climate inputs, and rules of thumb tie into the size and ventilation tools on this hub. Start with the authority guide, then use calculators below.
HVAC Sizing Guide
Industrial cooling load methodology, rules of thumb vs detailed methods, climate inputs, and verification—the canonical HVAC sizing reference on CalcPanel.
Open HVAC Sizing Guide →How to Calculate HVAC Capacity
Step-by-step capacity estimation with calculator links—worked inputs for workshop and utility-room screening.
How to Calculate HVAC Capacity →Core Tools
HVAC Size Calculator
Estimate cooling and heating load in tons, BTU/h, and kW from floor area, occupancy, and climate.
Use Calculator →ACH to CFM Calculator
Convert air changes per hour and room volume to CFM, m³/h, and L/s for fan and duct screening.
Use Calculator →HVAC Duct Size Calculator
Convert CFM and design velocity into duct area, round diameter, or rectangular trunk size (velocity method).
Use Calculator →HVAC Duct Static Pressure Calculator
Estimate duct friction rate and external static pressure from CFM, duct size, length, and fittings.
Use Calculator →HVAC Fan Laws Calculator
Scale fan CFM, static pressure, and brake HP with affinity laws from RPM or target airflow.
Use Calculator →Chiller Tonnage Calculator
Screen chilled-water plant tons from GPM × ΔT or known cooling load BTU/h—with an explicit safety factor.
Use Calculator →Psychrometric Calculator
Dew point, wet bulb, humidity ratio, and approximate enthalpy from dry-bulb and relative humidity.
Use Calculator →Calculation Workflow
- Recommended full flow: HVAC size → chiller tonnage (CHW plant) → psychrometrics → ACH to CFM → HVAC duct size → duct static pressure → fan laws → Industrial HVAC Design → Energy Estimator → verify kW on Factory Load.
- Size-first path: HVAC size calculator → How to Calculate HVAC Capacity → re-run size with safety margin.
- Ventilation-first path: ACH to CFM → duct size → static pressure → HVAC size when you also need tonnage context.
- Shortcut (approximate): HVAC size → Energy Estimator when you skip formal CFM and duct checks.
HVAC planning topics
Beyond the core calculators, these topics cover sq ft sizing, climate bands, ventilation, duct diameter, and handoff to Power tools for electrical and energy impact.
- Cooling sizeTons, BTU/h, IECC climate zone, HVAC size calculator
- PsychrometricsDew point, wet bulb, humidity ratio
- VentilationACH to CFM, room volume, fan CFM / fan laws
- Duct / trunk sizeCFM to diameter, static pressure, velocity method
- Sq ft & climateFloor area, climate zone, duct CFM routing
- Power Systems hubFactory load and feeder planning with HVAC kW
- Guides librarySizing methodology, load vs capacity, industrial design
Cooling size (area → tons → BTU/h)
Screen block cooling and heating load before Manual J or stamped engineering—one calculator, this hub. Sq ft rules and IECC zone factors live on the size calculator Formula section and FAQ.
- HVAC size calculator — tons, BTU/h, and kW from area, height, occupancy, IECC zone
- How to Calculate HVAC Capacity — worked examples and assumptions
- HVAC Load vs Capacity — difference for procurement conversations
Guides: HVAC Sizing Guide · Capacity calculation examples · Common sizing mistakes
Psychrometrics (dew point · wet bulb · enthalpy)
When moisture or coil leaving conditions matter, screen air-state properties before locking tonnage or outdoor-air strategy.
- Psychrometric calculator — dew point, wet bulb, humidity ratio, approximate enthalpy from dry-bulb and RH
- HVAC size calculator — return to tons / BTU/h after moisture context is set
Ventilation (ACH → CFM)
After tonnage context (or in parallel), convert target air changes and room volume into supply airflow for fans.
- ACH to CFM calculator — CFM, m³/h, and L/s from floor area, ceiling height, ACH
- HVAC fan laws calculator — scale CFM, SP, and BHP when RPM or target airflow changes
- Industrial HVAC Design — duct distribution and plant layout context
Duct / trunk size (CFM → diameter → ESP)
When CFM is known, screen free area and round or rectangular size with the velocity method, then friction/ESP—not Manual D.
- HVAC duct size calculator — area, round Ø, or rectangular sides from CFM and ft/min
- HVAC duct static pressure calculator — friction rate and duct + fitting ESP screen
- Industrial HVAC Design — duct sizing — velocity bands and plant narrative
Use Cases
- Factory workshop cooling: screen tonnage with the HVAC size calculator during process line expansion—see HVAC Sizing Guide for load breakdown.
- Electrical utility room: validate heat rejection and ventilation CFM before feeder upgrades on the Electrical hub.
- Facility retrofit bidding: quick cooling baseline plus energy cost screening before vendor shortlist.
Which HVAC Calculator Should You Use?
| Goal | Recommended Tool or Guide |
|---|---|
| Estimate cooling size / tonnage / BTU/h | HVAC size calculator |
| HVAC size by square feet | HVAC size calculator (sq ft rules in tool FAQ) |
| HVAC size by climate zone | HVAC size calculator (IECC zone dropdown) |
| Understand load vs installed capacity | HVAC Load vs Capacity Guide |
| Recheck after occupancy or process heat change | HVAC size calculator + How to Calculate HVAC Capacity |
| Dew point / wet bulb / humidity ratio | Psychrometric calculator |
| BTU/h ↔ tons conversion | HVAC size calculator (built-in converter) |
| Duct / trunk size from CFM | HVAC duct size calculator |
| Duct friction / external static pressure | HVAC duct static pressure calculator |
| Fan speed / affinity laws (CFM, SP, HP) | HVAC fan laws calculator |
| Chiller plant tons (GPM × ΔT) | Chiller tonnage calculator |
| Diffuser / grille free area | HVAC duct size (diffuser table) |
| Duct airflow (ACH → CFM) screening | ACH to CFM calculator |
| Plant-wide electrical impact of HVAC kW | Power Calculator → Factory Load |
| Annual HVAC operating cost | Industrial Energy Estimator |
Merge note: This hub (/hvac-calculator) is the primary URL for generic “HVAC calculator” planning. Task-specific tools (HVAC size, ACH to CFM) own their head-term SERP pages—use this hub when the query is broad, then drill into the matching calculator above.
HVAC Sizing Long-Tail Queries (Square Feet, Climate, Duct)
Generic “HVAC size calculator by zip code” queries route to the HVAC size calculator. Separate hvac duct size calculator intent uses the duct size tool—not as thin house/filter pages.
- Square feet / system / unit size: HVAC size calculator — also covers calculate hvac size, hvac system size calculator, and hvac unit size calculator.
- Zip code / climate: Pick your IECC climate zone on the size calculator—see the zone → factor table in that page’s Formula section.
- Duct / trunk size: Get CFM with ACH to CFM, diameter with HVAC duct size calculator, then ESP with duct static pressure; use fan laws for RPM/VAV changes.
Deep methodology: How to Calculate HVAC Capacity · HVAC Sizing Guide.
Related Guides
Partner Hub: Power Systems
HVAC kW feeds into facility demand and feeder sizing. Use the Power Calculator hub for factory load roll-up, transformer and generator context, and the Electrical hub for breaker and cable checks on HVAC feeders.
FAQ
What is an HVAC calculator used for?
This hub helps you pick the right free tool—cooling size (tons, BTU/h) or ventilation (CFM)—before detailed HVAC engineering. It does not replace Manual J or stamped loads for permit drawings.
Which HVAC calculator should I start with first?
For tonnage or BTU/h, start with the HVAC size calculator. For fan or duct airflow, start with ACH to CFM. Return to this hub when you need the full workflow.
Is there an HVAC size calculator by square feet?
Yes—use the HVAC size calculator with your floor area. The tool lists common BTU/h per square foot rules of thumb for US budgeting in its FAQ.
Can I size HVAC by zip code or climate zone?
Select your IECC climate zone on the HVAC size calculator. Zip-specific Manual J data still requires local design temperatures for permit drawings.
Which tool covers HVAC duct size or CFM?
Estimate tonnage on the HVAC size calculator first; then use ACH to CFM for airflow, duct size for diameter (includes diffuser/grille face-area screen), duct static pressure for ESP, and fan laws for RPM/VAV scaling. For chilled-water plant tons use the chiller tonnage calculator.
Do you have refrigerant charge or SEER savings calculators?
No dedicated tools—those SERPs are OEM line-charge apps and residential SEER shopping. For facility energy use, continue with the energy estimator; for capacity keep using HVAC size.
What is the difference between this hub and the HVAC size calculator?
This page (/hvac-calculator) is the HVAC calculators hub for navigation and workflow. The HVAC size calculator is the interactive tool for tons, BTU/h, and kW results—use it when your query is task-specific (size, capacity, sq ft).
How to calculate HVAC capacity for workshop retrofit?
Start with area and thermal assumptions in the HVAC size calculator, then update occupancy, process heat, and ventilation. See How to Calculate HVAC Capacity for worked steps.