# Greenheck Toolbox > HVAC fan law calculator and duct sizing tool. (iPhone/iPad app by Greenheck.) - Source: https://appshunter.io/ios/app/greenheck-toolbox/id526779916 (this page in markdown: same URL + `.md`) - Developer: [Greenheck](https://appshunter.io/developer/526779919) - Category: Utilities, Business - Price: Free - Rating: 3.00/5 from 3 App Store ratings · 9 written reviews indexed - Age rating: 4+ - Requires: iOS 7.0 · 2 MB - Languages: American English - Released: 2012-05-18 - Data updated: 2026-06-05 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/greenheck-toolbox/id526779916/reviews.md ## What is Greenheck Toolbox? Greenheck’s Toolbox includes a Fan Law Calculator and a Ductulator App. To use the Fan Law Calculator, input existing rpm, cfm, static pressure, and horse power. Modify any one measurement and the remaining three calculate. Greenheck’s Ductulator app allows you to quickly and easily size HVAC duct. Input your duct shape, rounded dimension, air temperature, elevation and select roughness. Next determine sizing by airflow or dimensions, select velocity or friction factor, input your volume, velocity, aspect ratio and calculate. Your results will be displayed. ## Key features - Fan Law Calculator - Ductulator App - Adjust fan performance - Size HVAC ductwork - Calculate airflow - Determine duct dimensions ## Recent user reviews (9 of 9) All indexed reviews: https://appshunter.io/ios/app/greenheck-toolbox/id526779916/reviews.md ### 1/5 — App Stopped Working *2020-07-13* Tried to use the app today (7-12-20) and it doesn’t work. ### 3/5 — Works most of the time *2017-01-30* I mainly use this app for its ductulator feature. It works most of the time but the app does have its bugs. Lately, the app will crash when selecting to size the duct through the airflow and friction factor parameters. It is the friction factor parameter that causes the app to crash. The app is not reliable but it's great for a quick reference when it works. ### 3/5 — Help with crash *2016-10-20* Hi, the app has a problem when I want to use the method of select the ducts based on the CFM and the Roughness the app crash. Please, can you help me with that? Thanks ### 1/5 — Freezes every time *2014-05-22* Got it to work once. Seemed fairly accurate. Definitely not reliable as is. Freezes up every time. I do have an older iOS.... ### 1/5 — This app is absolutely horrible *2014-02-20* I would expect so much more from Greenheck. This app is totally unusable and the interface looks like it was designed by my 4 year old. Come on, now, and get some professionals to design this for you. Pathetic. ### 1/5 — No good as is *2014-01-07* Had to delete! Kept freezing up me whole phone! The few times it did work it was spot on! Fix please.....would love to keep using! ### 1/5 — Not very practical *2012-12-19* User interface is very cumbersome. ### 1/5 — Disappointment *2012-11-20* I have to say I expected more when I saw the Greenheck name. Ductulator needs to allow the user to set a duct height and should provide sizing for 1:1 thru 5:1 automatically with an alternate spot to enter anything more extreme. ### 1/5 — Poorly thought out, not useful *2012-09-19* Fan law function has few real world uses, especially if used in the field. One must know brake horsepower to run the calc. Who has that information in hand if one does not have submittal or fan curve in front if them? This functions is not applicable for typical VAV systems with a duct static pressure control set point. Without this, erroneous fan power, as well as fan rpm, will result. The ductulator needs a major overhaul. Good thing it is free...that is what it is worth. ## Frequently asked questions about Greenheck Toolbox ### What are the main functions of Greenheck Toolbox? Greenheck Toolbox offers two primary functions: a Fan Law Calculator to adjust fan performance based on speed changes and a Ductulator to size HVAC ductwork by inputting various parameters like shape, dimensions, and airflow. ### How does the Fan Law Calculator work in Greenheck Toolbox? You input existing values for RPM, CFM, static pressure, and horsepower. By modifying any one of these measurements, the other three are automatically recalculated, allowing for quick adjustments to fan performance. ### What information is needed to use the Ductulator in Greenheck Toolbox? To use the Ductulator, you need to input duct shape, rounded dimension, air temperature, elevation, and select roughness. You can then determine sizing by airflow or dimensions, selecting velocity or friction factor, and inputting volume, velocity, and aspect ratio. ### Is Greenheck Toolbox available on Android devices? Based on the provided data, Greenheck Toolbox is supported on iPhone, iPad, and iPod devices. Information regarding Android compatibility is not available. ### How often is Greenheck Toolbox updated? The latest version of Greenheck Toolbox is 1.5, which was last updated on November 13, 2015. This indicates infrequent updates in recent years. ### What is the user rating for Greenheck Toolbox? Greenheck Toolbox has a user rating of 3.0 stars based on 3 ratings. This suggests a mixed reception from its user base. ### Does Greenheck Toolbox have ads? No, Greenheck Toolbox does not contain advertisements. The app is free to download and use without any ad interruptions. ### What is the age rating for Greenheck Toolbox? Greenheck Toolbox has an age rating of 4+. This means it is suitable for users aged 4 and above. ## Version history (last 5 releases) ### 1.5 — 2015-11-13 This app has been updated by Apple to display the Apple Watch app icon. General improvements ### 1.3.1 — 2013-08-26 Improvements ### 1.3 — 2012-11-10 iPad support ### 1.2 — 2012-09-17 Bug Fixes ### 1.1 — 2012-07-20 Added the "Ductulator" Calculator ## Apps similar to Greenheck Toolbox | App | Rating | Price | Category | | --- | --- | --- | --- | | [Digiduct](https://appshunter.io/ios/app/digiduct/id6738926359) | 5.0 (10) | Free | Utilities | | [AI Ductulator](https://appshunter.io/ios/app/ai-ductulator/id986252467) | 3.9 (9) | $3.99 | Utilities | | [Melink Cx](https://appshunter.io/ios/app/melink-cx/id1572479180) | — | Free | Utilities | | [Duct Calculator Elite](https://appshunter.io/ios/app/duct-calculator-elite/id665701601) | 4.8 (220) | $6.99 | Utilities | | [Allday HVAC Calc](https://appshunter.io/ios/app/allday-hvac-calc/id6446276144) | 5.0 (1) | Free | Utilities | | [Duct Calculator S&P](https://appshunter.io/ios/app/duct-calculator-s-and-p/id1096043356) | 5.0 (1) | Free | Utilities | ## More apps by Greenheck - [Greenheck Events](https://appshunter.io/ios/app/greenheck-events/id1434599148) - [Vari Green Drive 100+](https://appshunter.io/ios/app/vari-green-drive-100-plus/id1437558088) - [Greenheck Events](https://appshunter.io/ios/app/greenheck-events/id6479068155) All apps by Greenheck: https://appshunter.io/developer/526779919 ## Related topics [duct calculator for hvac installations](https://appshunter.io/ios/topics/duct-calculator-for-hvac-installations) --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-05.*