Deterministic Engineering Calculators for Ductwork, Loads & Diagnostics
Transparent engineering formulas built on ASHRAE, ACCA, EPA, and IECC standards.
The Connected HVAC Ecosystem
One Unified Building Science Architecture
Thermal load calculations, airflow distribution, refrigeration diagnostics, and envelope physics work in one continuous engineering chain:
1. Whole-Home Heat Load
Calculate sensible heat gains, solar transmission, and ACCA Manual J/S cooling equipment capacity.
2. Ductwork & Airflow Distribution
Size round and rectangular trunks, compute static friction loss, and derate flexible duct sag.
3. Refrigeration Diagnostics
Verify subcooling and target superheat against NIST REFPROP PT saturation curves for R-410A & R-454B.
4. Heat Pump Electrification
Size heat pumps, calculate heating balance points, and optimize winter supplemental heating.
5. Thermal Envelope & Codes
Calculate series and parallel wall assembly R-values complying with IECC climate zone energy codes.
Complete Engineering Suite
All 21 HVAC Engineering Calculators
Select a category or search below to launch any calculator with prefilled engineering presets:
Digital Ductulator & Air Duct Sizing Tool
Professional online ductulator for HVAC engineers and technicians. Size round, rectangular, and flat oval ductwork using standard equal friction equations.
Flexible Duct CFM & Friction Drop Chart
Interactive flexible duct CFM capacity chart across standard diameters (4" to 20") with real-world installation sag and compression derating.
HVAC CFM & Airflow Calculator
Calculate HVAC airflow (CFM) using the sensible heat equation, duct velocity and area, room air changes per hour (ACH), or cooling tonnage rules.
Kitchen Range Hood CFM & Make-Up Air Sizer
Calculate required kitchen range hood CFM for gas and electric cooktops. Check mandatory IRC Section M1503.6 make-up air code requirements.
Duct Friction Loss & Total Equivalent Length (TEL) Sizer
Calculate ACCA Manual D Total Equivalent Length (TEL), Available Static Pressure (ASP), and Design Friction Rate (FR) for residential duct design.
MERV Air Filter Sizing & Static Pressure Drop Sizer
Calculate HVAC air filter face velocity (FPM) and static pressure drops across 1-inch, 2-inch, and 4-inch deep MERV 8 to MERV 16 pleated media.
BTU Heating & Cooling Load Calculator
Estimate whole-home and room heating and cooling loads (BTU/hr and Tons) based on square footage, climate zone, insulation quality, and window exposure.
AC Tonnage & Room Capacity Calculator
Match room and home square footage to required air conditioning tonnage (1.5 to 5.0 Tons) with regional climate adjustments and SEER2 operating cost modeling.
HVAC Model Number Tonnage Decoder
Instant HVAC model number decoder. Enter the model string on your Carrier, Trane, Goodman, Lennox, Rheem, or York nameplate to find its tonnage and BTU rating.
Mini-Split Multi-Zone Sizing Calculator
Size multi-zone ductless mini-split systems. Match room heat loads to indoor wall/cassette heads (6k to 24k BTU) and outdoor multi-port condensers.
Target Superheat & Subcooling Charging Calculator
Calculate target superheat (fixed orifice) and target subcooling (TXV) across R-454B, R-32, R-410A, and R-22 with EPA fault isolation guidance.
Digital Refrigerant Pressure-Temperature Chart
High-precision digital Pressure-Temperature chart for R-454B, R-32, R-410A, R-22, R-134a, R-404A, and R-407C with bubble and dew point curve toggles.
Psychrometric Chart & Moist Air Calculator
Calculate moist air thermodynamic properties from any 2 inputs (Dry Bulb, Wet Bulb, Dew Point, RH, Enthalpy) with altitude barometric compensation.
Refrigerant Line Set Charge & Weigh-In Calculator
Estimate the manufacturer-specified initial refrigerant weigh-in adjustment for R-454B, R-32, and R-410A line sets using sourced OEM profiles.
Heat Pump Sizing & Balance Point Tool
Calculate heat pump thermal balance point, cold-climate low-ambient heating capacity (47°F, 17°F, -5°F), and auxiliary electric backup heat strip sizing.
Furnace Sizing & AFUE Efficiency Calculator
Calculate required furnace input and output BTU based on home square footage, climate zone, and AFUE efficiency (80% vs 96% condensing).
Hydronic Boiler & Baseboard Sizing Calculator
Size residential hydronic heating boilers based on fin-tube baseboard linear footage, cast-iron radiator EDR, and indirect domestic hot water priority.
Garage & Workshop Heater Sizing Calculator
Size gas unit heaters, forced-air electric heaters, and radiant tubes for attached and detached garages accounting for slab losses and door infiltration.
Combustion Air & Confined Space Sizer (NFPA 54 / IFGC)
Calculate mechanical room confined space volume (50 cu ft/1,000 BTU) and size permanent combustion air openings for gas furnaces and water heaters.
Insulation R-Value & U-Factor Calculator
Build multi-layer wall, roof, and floor assemblies to calculate total R-value (R-total) and overall U-factor with IECC 2021/2024 climate zone compliance checks.
Building Heat Loss & Infiltration Calculator
Calculate whole-building peak heat loss combining envelope conductive transmission (U * A * Delta T) and blower door air infiltration leakage.
Engineering Transparency
Built on Open Engineering Standards
Deterministic thermodynamic and fluid mechanics formulas with transparent physical assumptions:
ASHRAE & ACCA Validated
Colebrook equal friction duct equations and ACCA Manual J/S/D sizing compliance with zero ad-hoc heuristics.
NIST REFPROP Thermodynamics
Precision saturation tables for next-gen A2L refrigerants (R-454B, R-32) with discrete bubble and dew temperature glide modeling.
Zero Paywalls & No Lead-Gen
100% free, client-side engineering tools with instant permalink sharing, iframe embeds, and printable calculation submittals.
IECC Energy Code Compliance
Continuous exterior insulation and thermal bridging calculations conforming to 2021/2024 International Energy Conservation Codes.
Engineering FAQ
Frequently Asked Questions
Key technical specifications, engineering methodologies, and standards compliance:
Airflow & DuctsCooling LoadsField DiagnosticsHeating SystemsBuilding Science