Deterministic Engineering Calculators for Ductwork, Loads & Diagnostics
Transparent thermodynamic and fluid mechanics formulas referenced from ASHRAE, ACCA, NFPA, and building energy codes. Client-side calculations.
Top Engineering Calculators
Instant 1-tap access to featured HVAC sizing, airflow, and refrigerant diagnostic tools:
The Connected HVAC Ecosystem
One Unified Building Science Architecture
Thermal load calculations, airflow distribution, refrigeration diagnostics, and envelope physics work in one continuous engineering workflow:
Whole-Home Heat Load
Calculate sensible heat gains, solar transmission, and ACCA Manual J/S cooling equipment capacity.
Ductwork & Airflow
Size round and rectangular trunks, compute static friction loss, and derate flexible duct sag.
Refrigeration PT
Verify subcooling and target superheat against refrigerant saturation property references for R-410A & R-454B.
Heat Pump Electrification
Size heat pumps, calculate heating balance points, and optimize winter supplemental heating.
Thermal Envelope
Calculate series and parallel wall assembly R-values and compare against IECC and ASHRAE 90.1 criteria.
Complete Engineering Suite
All 25 HVAC Engineering Calculators
Select a category or search below to launch any calculator with prefilled engineering presets:
Digital Ductulator & Air Duct Sizing Tool
Free online ductulator for HVAC duct sizing. Size round and rectangular air ducts via equal friction and Huebscher's formula. Real-time 2D visualizer.
Flexible Duct CFM & Friction Drop Chart
Flexible duct CFM chart for 4-in to 20-in ducts. Compare airflow across 0.05–0.15 in. wg friction with modeled 0%–30% sag deratings from ASHRAE RP-1333 data.
HVAC CFM & Airflow Calculator
Calculate HVAC airflow (CFM) from duct size, velocity (FPM), sensible load (1.08 × ΔT), room ACH, or tonnage benchmarks. Runs locally in your browser.
Kitchen Range Hood CFM & Make-Up Air Sizer
Size kitchen range hood CFM for gas and electric cooktops using HVI width guidance. Evaluate make-up-air requirements under applicable IRC provisions.
Duct Friction Loss & Total Equivalent Length (TEL) Sizer
Calculate duct friction loss rate using Darcy-Weisbach and Colebrook models. Evaluate Available Static Pressure (ASP) and design friction rate concepts.
Equivalent Length & Total Effective Length (TEL) Calculator
Calculate duct Total Effective Length (TEL) and fitting equivalent lengths referencing ACCA Manual D methodology to determine design friction rates.
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
Estimate residential AC cooling capacity (1.5 to 5.0 Tons) and SEER2 operating costs using regional climate factors and ceiling height adjustments.
HVAC Model Number Tonnage Decoder
Decode supported manufacturer model-number patterns (Carrier, Trane, Lennox, Goodman, Rheem, Daikin) to identify nominal tonnage, BTU capacity, and series.
Mini-Split Multi-Zone Sizing Calculator
Estimate multi-zone ductless mini-split sizing. Match room screening loads to candidate indoor heads (6k to 24k BTU) and supported outdoor unit configurations.
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 field diagnostic guidance.
Digital Refrigerant Pressure-Temperature Chart
Interactive refrigerant Pressure-Temperature (PT) chart for R-454B, R-32, R-410A, R-22, and zeotropic blends. Instant bubble and dew point saturation lookups.
Psychrometric Chart & Moist Air Calculator
Calculate moist air thermodynamic properties from supported input pairs (DB+RH, DB+WB, DB+DP) with barometric altitude adjustment.
Refrigerant Line Set Charge & Weigh-In Calculator
Calculate OEM-specified line-set refrigerant charge adjustments and weigh-in targets for R-454B, R-32, and R-410A using verified manufacturer data.
Heat Pump Sizing & Balance Point Tool
Calculate heat pump thermal balance point, cold-climate heating capacities (47°F, 17°F, 5°F), aux heat strip sizing (kW), and dual-fuel economic crossover.
Furnace Sizing & AFUE Efficiency Calculator
Estimate residential furnace sizing, heating BTU requirements, and AFUE efficiency (80% vs 96% condensing) based on home area, climate zone, and envelope.
Hydronic Boiler & Baseboard Sizing Calculator
Calculate hydronic boiler sizing, required DOE heating capacity, fin-tube baseboard BTU/ft, radiator EDR, and I=B=R piping/pickup factors.
ASHRAE Hydronic Expansion Tank Sizing Calculator
Size closed-loop diaphragm and bladder expansion tanks using ASHRAE technical references with optional commercial vessel rating considerations.
Garage & Workshop Heater Sizing Calculator
Size gas unit heaters, forced-air electric heaters, and radiant tubes for 1 to 3-car garages. ACCA Manual J & ASHRAE heat loss with slab insulation derating.
Combustion Air & Confined Space Sizer (NFPA 54 / IFGC)
Evaluate mechanical room combustion air openings under NFPA 54 and IFGC reference methods, including standard 50 cu ft/1,000 BTU confined space checks.
Thermal Bridging & Effective R-Value Calculator
Estimate whole-wall effective R-value and assembly U-factor accounting for framing thermal bridging referencing ASHRAE 90.1 Appendix A and IECC.
Insulation R-Value & U-Factor Calculator
Build multi-layer wall, roof, and floor assemblies to calculate 1-D series R-value (R_stack) and overall U-factor with selected IECC reference benchmarks.
Building Heat Loss & Infiltration Calculator
Estimate whole-building peak heat loss combining envelope conductive transmission (U * A * Delta T), slab perimeter F-factors, and air infiltration leakage.
Heat Pump Auxiliary Electric Heat Strip Sizing Calculator
Estimate heat pump auxiliary electric heat strip deficit (kW), emergency backup sizing, NEC Article 424 circuit ampacity guidelines, and temperature rise.
Featured HVAC Engineering Guides
Deep-dive technical breakdowns connecting governing equations (Darcy-Weisbach, Manual J/S, Hyland-Wexler) to practical field sizing and diagnostics.
Air Distribution & Duct Hydraulics
Comprehensive fluid mechanics reference for sizing HVAC supply and return ductwork, evaluating Colebrook-White friction rates, Huebscher equivalent diameters, and ACCA Manual D available static pressure workflows.
ACCA Manual J & S Cooling Load Guide
Deterministic methodology for calculating peak residential sensible and latent cooling loads, evaluating Sensible Heat Ratios (SHR), and selecting equipment matching expanded manufacturer performance tables.
Heating Systems & Heat Pump Sizing
Engineering principles of residential heating, cold-climate air-source heat pump COP derating curves, auxiliary strip staging, hydronic condensing boiler dew points, and NFPA 54 combustion air sizing.
Engineering Transparency
Built on Open Engineering Standards
Deterministic thermodynamic and fluid mechanics formulas with transparent physical assumptions:
ASHRAE & ACCA References
Implements Colebrook-White equal friction duct equations and equipment sizing methods based on ACCA Manual J, S, and D references.
NIST REFPROP Property Data
Refrigerant thermodynamic and saturation properties referenced from NIST REFPROP data models, including zeotropic glide curves.
In-Browser Execution
Client-side calculation engines with zero required user accounts, instant permalink sharing, iframe embeds, and printable submittals.
IECC & ASHRAE 90.1 Criteria
Compares calculated wall and roof assembly R-values and thermal bridging deratings against configured IECC and ASHRAE 90.1 criteria.
Engineering FAQ
Frequently Asked Questions
Key technical specifications, engineering methodologies, and standards compliance: