Two vs Duct Calculator
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Two
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Stop searching. Access instantly with colors and numbers. Photos, videos, precious memories. Are they lost somewhere in your phone? With "2 STEPS", you can directly access your important content with just two taps. Dead Simple to Use 1. Pick a color (choose from 10) 2. Tap a number (1 to 10) That's it! No more opening folders, scrolling endlessly, searching... All that hassle is gone. Use It Your Way ・Family photos on "Red 1" ・Favorite YouTube videos on "Blue 3" ・Important documents on "Green 5" ・Your favorite content on "Purple 7" Create your own color-number combinations with 100 shortcut slots at your fingertips. Key Features ・Save and view photos & images ・Play YouTube videos directly ・You can register and play Spotify songs. However, upon the first use after launching the app, you will be redirected to the Spotify screen where the song will be played. From the second time onwards, you can control playback within this app. ・Intuitive color-coded organization ・Dark mode support ・Clean, beautiful design Perfect For You If You ・Want to organize your digital life ・Need quick access to frequent content ・Often show photos to family and friends ・Love simple, elegant apps ・Want to try a fresh organization method Premium Features Free: 3 slots per color (15 total) Premium: All 10 colors × 10 slots (100 total) Transform your mobile experience with the magic of colors and numbers. Download now and start your 2-step journey today!
Duct Calculator
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Size HVAC ductwork or check an existing duct, then save the calculation for the job. Enter airflow and a design friction rate to get round and rectangular sizes that meet both the friction limit and the residential velocity guide. Save the inputs and results on your device. You can reopen them on site or share a text report. Ductulator requires a subscription to use its tools. Eligible new subscribers can start with a free trial: 7 days on the yearly plan or 3 days on the monthly plan. The subscription renews automatically unless canceled in Apple Account settings. Your subscription includes Size a new duct - Recommended round and rectangular sizes that meet your design friction rate and the velocity guide - A separate label for the round diameter based on friction alone - Set one rectangular side and calculate the other - Air velocity and actual friction at the recommended sizes - Supply and return settings, with a design friction rate you can set yourself Fit available space - Enter maximum inside height and width - Compare rectangular options that meet your friction and velocity limits - Search a 2-inch size grid from 4 to 60 inches; confirm fabrication availability - Send an option to Check and save it with your job - Allow for insulation and supports outside the entered dimensions Check an existing duct - Enter a round diameter or rectangular width and height - Calculate velocity, friction rate and capacity at the entered conditions - See whether the duct is adequate for the requested airflow - Use an undersized duct's inputs to find a suitable size, or send a recommended round size to Check Work out your friction rate - Calculate friction rate from available static pressure and total effective length - Apply the result directly to the calculator - Keep your chosen design rate when switching between supply and return - Help with what to enter for pressure and effective length Save calculations by job - Restore the last valid calculation when you reopen the app - Browse the last 20 completed calculations - Save named calculations with a project and notes - Reopen the inputs while keeping the original saved report unchanged - Share a saved report as text Materials and calculation method - Galvanized sheet metal, duct board and flexible duct - Flex sized as installed: fully stretched or 4%, 15% or 30% compressed, with ASHRAE's pressure drop correction - Darcy-Weisbach with the Colebrook friction factor - Huebscher equivalent round diameter for rectangular ducts - Standard air at 70 degrees F and sea level - Residential velocity guide: 900 fpm supply and 700 fpm return Units are CFM, inches, feet, fpm and inches of water per 100 feet. Results describe the conditions you enter; the app does not measure airflow. You supply the pressure and fitting-length data for the friction worksheet. It does not produce a complete Manual D design or correct for altitude. Calculations and saved jobs stay on your device unless you choose to share a report. You do not need an account. Deleting the app removes its local data. Terms: https://ductulator.vovaluka.com/terms Privacy: https://ductulator.vovaluka.com/privacy
Screenshots
Verdict
The clearest difference is update cadence: Two at every 2 days against Duct Calculator's fortnightly. On price, 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
Both are free to download. Two sells 2 in-app purchases, starting at $0.99 per month and Duct Calculator sells 1 in-app purchase, starting at $9.99 per year. Whichever you choose, the download price is not the number that matters.
Two ships an update every 2 days, Duct Calculator fortnightly. The most recent releases landed on October 28, 2026 and October 20, 2026 respectively.
| Parameter | Two | Duct Calculator |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 2 days — better | Fortnightly |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Devices | iPhone | iPhone |
| Requires iOS | 18.5 | 17.0 — better |
| Further details — not scored | ||
| Size | 4 MB | 8 MB |
| Age rating | 4+ | 4+ |
| Developer | Takahiro Ando | Vladimir Lukashov |
In-app purchases
Two
- Premium Access - Monthly7 Days trial$0.991 Month
- Premium Access - Yearly7 Days trial$6.991 Year
Duct Calculator
- Ductulator Pro$9.991 Year









