Comparison

Ruler vs Ductulator

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

Head to head
About

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.

Highlights
  • 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
Features
Read full description

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.

About

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.

Highlights
  • 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
Features
Currently charting
Read full description

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

Ruler4 screens
Ductulator4 screens

Verdict

The call

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

CostPrice · In-app purchases · Ads · Monetization

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.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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.

Scorecard10 real differences · 1 level
Ruler versus Ductulator: the parameters behind the verdict, then further details
ParameterRulerDuctulator
PriceFree — better$3.99
Rating3.7 (3 ratings)4.7 (353 ratings) — better
Positive reviews63.0% of reviews — better50.0% of reviews
Number of ratings3353 — better
Update frequencyEvery 5 monthsEvery 2 months — better
AdsYesNo — better
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree — better
Best chart rank—#74 — better
DevicesiPhone, iPad, iPod — betteriPhone, iPad
Requires iOS15.0 — better18.6
Further details — not scored
Size4 MB1 MB
Age rating4+4+
Developermitsunori oishiWassim Murr

Customer experience

Ruler

All ratings3 ratings
Positive66.7%
Neutral0.0%
Negative33.3%
Written reviews27 reviews
Positive63.0%
Neutral3.7%
Negative33.3%

Ductulator

All ratings317 ratings
Positive93.4%
Neutral2.2%
Negative4.4%
Written reviews22 reviews
Positive50.0%
Neutral13.6%
Negative36.4%

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

1 purchases

Ruler

One-time1
  • Hide Ads$0.99
None

Ductulator

No in-app purchases

Questions

Is Ruler free?
Ruler is free to download, with in-app purchases available.
Is Ductulator free?
Ductulator costs $3.99, with no in-app purchases.
Which has better reviews, Ruler or Ductulator?
Ductulator is rated higher. Ruler averages 3.7 out of 5 from 3 ratings, while Ductulator averages 4.7 from 353 ratings.
Do Ruler or Ductulator have ads?
Ruler shows ads; Ductulator does not.
Which is updated more often, Ruler or Ductulator?
Ruler ships an update every 5 months, and Ductulator every 2 months. Most recently, Ruler was updated on October 21, 2026 and Ductulator on October 24, 2026.

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