Comparison

HVAC Formulator vs Duct Calculator

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

HVAC Formulator

This app provides HVAC professionals with over 900 essential formulas and calculations for load calculations and system design. It supports both US and Metric units, offers instant switching, and includes 23 calculator categories and over 460 unit conversions. Designed for field use, it works offline and allows users to save and share results.

Highlights
  • Over 900 formulas and calculations
  • US & Metric unit support
  • 23 calculator categories
  • 460+ unit conversions
  • 8 temperature scales
  • Offline functionality
  • Save and share results
Features
Read full description

HVAC FORMULATOR is the essential tool for Heating, Ventilating, and Air Conditioning professionals. With over 900 formulas and calculations, it covers everything from basic load calculations to advanced system design — all in your pocket. US & METRIC SUPPORT — Switch instantly between US (Imperial) and Metric (SI) units. Results display in both systems so you always have the value you need. Input labels and conversions update automatically. 23 CALCULATOR CATEGORIES including: - Cooling Load — Sensible, latent, and total cooling calculations, tons, EER, COP, and sensible heat ratio - Fan Laws — Speed and diameter affinity laws for CFM, pressure, and horsepower - Duct Sizing — Velocity, round and rectangular sizing, equivalent diameter, aspect ratio - Ventilation Rate — ASHRAE 62.1 breathing zone, air changes per hour, exhaust fan sizing - Electrical — Ohm's Law, single and three-phase power, motor FLA, watts to BTU/h - Gas Laws — Boyle's, Charles's, Gay-Lussac's, Combined, and Ideal Gas Law - Psychrometrics — Bypass factor, mixed air temperature, percent outside air, dew point - Hydronic Formulas — Heat transfer, flow rate, pipe velocity, expansion tank, Cv coefficient - Boiler — Efficiency calculations, BTU output, heat absorption - Refrigeration — Tonnage output, compression ratio, mass flow rate, COP - Ductwork — Velocity, velocity pressure, total pressure, equivalent round - Airside — Sensible heat, latent heat, total heat (US and Metric) - Piping — Pipe area, weight, friction loss, expansion, Hazen-Williams, 70+ formulas - Steam — Condensate loads, fuel calculations, steam flow - Pump Laws — Break horsepower, suction head, pump affinity laws - Energy — Fuel values for oil, gas, coal, propane, ethanol, and more - Heating Design — Electric heating, baseboard, radiant ceiling, boiler capacity, hydronic snow melting - Heating Requirement — Insulation-based load calculations - Humidity — Specific humidity, relative humidity, sensible and latent heat - Loads — Temperature loads, heat gains from lights, equipment, and machines - Temperature — Mixed air, liquid mixing, final temperature calculations - Waterside System — Total heat, evaporator and condenser flow rates - Air Change Rate — Air changes per hour, air flow rate 460+ UNIT CONVERSIONS across 16 categories: Metric, Pressures, BTU, Linear, Square, Cubic, Liquid Measures, Weights, Flows, Power, Horsepower, Watts, Hydraulic, Ft-Lbs, Sand/Volume, and HVAC-specific conversions. 8 TEMPERATURE SCALES — Convert between Celsius, Fahrenheit, Kelvin, Rankine, Reaumur, Newton, Delisle, and Romer. BUILT FOR PROFESSIONALS: - Search across all 900+ formulas instantly - Mark favorites for quick access - Save calculation history with full breakdown - Share and export results - Clean, fast interface designed for field use - Works offline — no internet required HVAC FORMULATOR is a professional-grade tool built for HVAC technicians, engineers, contractors, and students. New formulas and features are added regularly.

About

Duct Calculator

This professional HVAC utility assists engineers and technicians with precise duct sizing and airflow calculations for ventilation systems. It simplifies essential calculations for both design and installation work, improving on-site efficiency.

Highlights
  • Calculate duct sizes using airflow (CFM) and velocity (FPM)
  • Supports rectangular and round duct sizing in inches
  • Determine air flow rate in CFM
  • Calculate air velocity in FPM
  • Simple interface for fast on-site calculations
Features
Read full description

Duct Calculator is a focused duct sizing tool for HVAC engineers, designers and installation technicians. Enter what you know and get the duct dimensions, airflow or air velocity you need, without a chart or a slide rule. CALCULATIONS - Duct size: find the required duct dimensions from airflow (CFM) and air velocity (FPM). - Airflow: determine the airflow rate in CFM. - Air velocity: determine velocity in FPM to help verify system performance. DUCT SHAPES - Round ducts - Rectangular ducts - Results shown in inches WHO IT IS FOR - HVAC engineers and designers checking a duct size during design work. - Installation technicians and contractors who need a quick answer on site. - Students learning how airflow, velocity and duct size relate. WHERE IT HELPS - Sizing a new supply or return run from a known CFM. - Checking whether an existing duct keeps velocity within your target. - Comparing a round duct with a rectangular one when space is tight. SIMPLE BY DESIGN A clean interface with only the inputs you need, so you get an answer quickly on the job. Duct Calculator is free to use. An optional one-time upgrade removes ads. Results are intended as a calculation aid. Always confirm designs against applicable codes and project requirements. Download Duct Calculator and size your next duct run. Privacy Policy : https://semiconhub.in/manager/privacy.html Terms and Condition : https://semiconhub.in/manager/tcondition.html

Screenshots

HVAC Formulator4 screens
Duct Calculator4 screens

Verdict

The call

The clearest difference is price: Duct Calculator at Free against HVAC Formulator's $4.99. Duct Calculator also leads on rating (4.7 vs 2.0) and ratings volume (3 vs 1). HVAC Formulator's advantage is update cadence (every 2 months vs every 10 months). On ads, in-app purchases and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Duct Calculator is free to download; HVAC Formulator costs $4.99 up front. HVAC Formulator sells 1 one-off in-app purchase and Duct Calculator sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

ReceptionRating · Positive reviews · Number of ratings

Duct Calculator holds the better App Store score, 4.7 against 2.0. Both are backed by a comparable volume of ratings — 1 and 3 respectively.

UpkeepUpdate frequency

HVAC Formulator ships an update every 2 months, Duct Calculator every 10 months. The most recent releases landed on October 18, 2026 and October 26, 2026 respectively.

Scorecard6 real differences · 4 level
HVAC Formulator versus Duct Calculator: the parameters behind the verdict, then further details
ParameterHVAC FormulatorDuct Calculator
Price$4.99Free — better
Rating2.0 (1 ratings)4.7 (3 ratings) — better
Positive reviews9.1% of reviews—
Number of ratings13 — better
Update frequencyEvery 2 months — betterEvery 10 months
AdsNoNo
In-app purchasesYesYes
MonetizationPaidFree with in-app purchases — better
DevicesiPhone, iPadiPhone, iPad, iPod — better
Requires iOS18.615.6 — better
Further details — not scored
Size73 MB44 MB
Age rating4+4+
DeveloperHistorycentral.comSachinbhai Surani

Customer experience

HVAC Formulator

All ratings1 ratings
Positive0.0%
Neutral0.0%
Negative100.0%
Written reviews11 reviews
Positive9.1%
Neutral18.2%
Negative72.7%

Duct Calculator

All ratings3 ratings
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

1 purchases

HVAC Formulator

One-time1
  • HVAC Pro$3.99
1 purchases

Duct Calculator

One-time1
  • Lifetime premium$9.99

Questions

Is HVAC Formulator free?
HVAC Formulator costs $4.99, and also offers in-app purchases.
Is Duct Calculator free?
Duct Calculator is free to download, with in-app purchases available.
Which has better reviews, HVAC Formulator or Duct Calculator?
Duct Calculator is rated higher. HVAC Formulator averages 2.0 out of 5 from 1 ratings, while Duct Calculator averages 4.7 from 3 ratings.
Do HVAC Formulator or Duct Calculator have ads?
Neither HVAC Formulator nor Duct Calculator shows ads.
Which is updated more often, HVAC Formulator or Duct Calculator?
HVAC Formulator ships an update every 2 months, and Duct Calculator every 10 months. Most recently, HVAC Formulator was updated on October 18, 2026 and Duct Calculator on October 26, 2026.

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