Ruler vs Ductulator
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Ruler
This app displays various measurement scales for length, including meters and inches. It allows users to set magnification ratios and reduced scales for different applications. Users can calibrate the ruler and adjust PPI settings for accurate measurements.
- Display various measurement scales
- Set magnification ratios
- Set reduced scales
- Measure in meters and inches
- Free mode for custom scales
- Calibration for accuracy
- PPI setting
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Scale Ruler is the simple application to display the scale of various measurement units. ※ Warning: - The accuracy of the scales cannot be guaranteed. - Calibration and PPI values will be reset when the model changes. - Set the PPI value only when the model is undecided. - When you change the PPI value, perform calibration after the change. ■How to use: ■Select mode In UNLOCKED state, after choosing measurement unit, magnification ratio and reduced scale, the scale is displayed. ■Free mode When dragging the screen at UNLOCK, you can set the scale in the range 1: 1 to 1: 100. When you press and hold the scale value, the keyboard is displayed and you can enter the scale. You can lock the scale on the ruler with a switch. Sorry for the advertisement during unlocking. After In-App Purchase, your ads will no longer be displayed. Specification of Scale Ruler - measure length meter,inches - magnification ratio 50% , 70.7% , 100% , 141% , 200% - reduced scale for meter 1:100 , 1:150 , 1:200 , 1:250 , 1:300 , 1:400 , 1:500 , 1:600 for inch 1:1 , 1:1.5 , 1:2 , 1:2.5 , 1:3 , 1:4 , 1:5 , 1:6 for inch(Architectural) 1:1 , 1:2 , 1:4 , 1:8 , 1:12 , 1:16 , 1:24 , 1:32 , 1:48 , 1:64 1:96 , 1:128 , 1:192 , 1:384 for inch(Engineering) 1:120 , 1:240 , 1:360 , 1:480 , 1:600 , 1:720 1:800 , 1:960 , 1:1080 ■ Settings - Calibration - PPI (pixels per inch) setting - In-app purchase (ads not displayed) - In-app purchase restoration ■ Calibration Adjust the length of the ruler. Use the correct ruler for adjustment. "Calibration" button: Records the adjusted state and reflects the calibration result on the ruler. "Reset" button: Returns the adjustment status to the specified value. It will not be recorded. "Initialize" button: Returns the adjustment status to the specified value and reflects it on the ruler. * Caution: The calibration value will be reset when the model changes. ■ PPI (pixels per inch) setting If the model is undecided, check the PPI value of the model before setting the PPI value. * Please set only when the model is undecided. "OK" button: Record the entered PPI value and reflect it on the ruler display. "Initialize" button: Returns the PPI value to the specified value and reflects it on the ruler. * Caution: The PPI value will be reset when the model changes.
Ductulator
Instantly calculate HVAC duct sizes based on airflow, friction rate, or velocity. This tool provides accurate duct dimensions in seconds without needing charts, supporting various duct types and units.
- Instant duct sizing
- Friction rate or velocity calculation
- Multiple valid duct dimensions
- IP and SI units support
- Detailed sizing mode
- Rectangular, circular, and flexible ducts
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Size HVAC ducts instantly using airflow, friction or velocity. Get accurate duct dimensions in seconds — no charts required. • Get a range of suitable duct sizes based on friction rate or velocity. • Get multiple valid duct dimensions instantly. • Tap on Friction Rate or Velocity to toggle between calculation methods. • IP and SI units. • Detailed sizing mode to adjust the duct dimensions and air flow rates. • Supports rectangular, circular and flexible ducts. • Automatic friction and velocity updates. Calculations are based on standard air 0.075 lb/ft3 (1.2 kg/m3) in clean galvanized steel or non-metallic flexible ducts. Any feedback is welcome, and will be the basis for future updates.
Screenshots
Verdict
The clearest difference is price: Ruler at Free against Ductulator's $3.99. Ruler also leads on review sentiment (63% vs 50%) and iOS requirement (15.0 vs 18.6). Ductulator's advantage is rating (4.7 vs 3.7) and in-app purchases (none vs 1). On 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
Ruler is free to download; Ductulator costs $3.99 up front. Ruler sells 1 one-off in-app purchase. Ductulator asks for nothing beyond the download.
Ductulator holds the better App Store score, 4.7 against 3.7. That said, the two scores are not equally well evidenced: Ductulator has 353 ratings behind it against 3, so its average is the more settled of the two. Written reviews complicate that: 63% of Ruler's written reviews are positive against 50% of Ductulator's, so the app with the better star average is not the one people write more warmly about.
Ruler ships an update every 5 months, Ductulator every 2 months. The most recent releases landed on October 21, 2026 and October 24, 2026 respectively.
| Parameter | Ruler | Ductulator |
|---|---|---|
| Price | Free — better | $3.99 |
| Rating | 3.7 (3 ratings) | 4.7 (353 ratings) — better |
| Positive reviews | 63.0% of reviews — better | 50.0% of reviews |
| Number of ratings | 3 | 353 — better |
| Update frequency | Every 5 months | Every 2 months — better |
| Ads | Yes | No — better |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | Free — better |
| Best chart rank | — | #74 — better |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 15.0 — better | 18.6 |
| Further details — not scored | ||
| Size | 4 MB | 1 MB |
| Age rating | 4+ | 4+ |
| Developer | mitsunori oishi | Wassim Murr |
Customer experience
Ruler
Ductulator
Bugs and requests
Ruler
Not enough reviews yet to summarise bugs or requests.
Ductulator
Reported bugs
4 issues- Decimal point doesn't work on calculator
- New flex option isn't working properly
- Friction rate can't be changed in the latest version
- Skips duct sizes (e.g., 24-26)
Requested features
5 requests- Ability to pick duct size and see CFM
- Include flat oval ducts
- Option to select round or square duct
- Ability to enter duct size and get CFM
- Option for flex duct
In-app purchases
Ruler
- Hide Ads$0.99
Ductulator
No in-app purchases









