Comparison

Ruler vs CAL_

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

CAL_

Features
Read full description

CAL_ is the next evolution of calculators. Made especially for iPhone, it brings the venerable calculator to an all-new level. LOG FEATURE All of your calculations are logged, so you can refer to them at any time. Use the ANS key to bring up the most recent result from the log. You can toggle commas and decimal points, and also use a guide that shows you when your units are in the millions, billions, and beyond. CURRENCY CONVERSIONS Get real-time currency rates for up to three currencies at once. You can also see a graph of currency value fluctuations. UNIT CONVERSIONS Want to know how many Tokyo Domes there are to an acre? Or how many lbs make up a stone? It's right at your fingertips in CAL_.

Screenshots

Ruler4 screens
CAL_3 screens

Verdict

The call

The clearest difference is in-app purchases: CAL_ at none against Ruler's 1. CAL_ also leads on ads (none vs shown) and update cadence (every 4 days vs every 5 months). On price 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

Both are free to download. Ruler sells 1 one-off in-app purchase. CAL_ asks for nothing beyond the download.

UpkeepUpdate frequency

Ruler ships an update every 5 months, CAL_ every 4 days. The most recent releases landed on November 1, 2026 and October 29, 2026 respectively.

Scorecard4 real differences · 6 level
Ruler versus CAL_: the parameters behind the verdict, then further details
ParameterRulerCAL_
PriceFreeFree
Rating3.7 (3 ratings) — better—
Positive reviews63.0% of reviews—
Number of ratings3 — better—
Update frequencyEvery 5 monthsEvery 4 days — better
AdsYesNo — better
In-app purchasesYesNo — better
MonetizationFree with in-app purchases—
DevicesiPhone, iPad, iPod — betteriPhone, iPod
Requires iOS15.012.0 — better
Further details — not scored
Size4 MB9 MB
Age rating4+4+
Developermitsunori oishiSQUAIR Inc.

In-app purchases

1 purchases

Ruler

One-time1
  • Hide Ads$0.99
None

CAL_

No in-app purchases

Questions

Is Ruler free?
Ruler is free to download, with in-app purchases available.
Is CAL_ free?
CAL_ is free to download, with no in-app purchases.
Do Ruler or CAL_ have ads?
Ruler shows ads; CAL_ does not.
Which is updated more often, Ruler or CAL_?
Ruler ships an update every 5 months, and CAL_ every 4 days. Most recently, Ruler was updated on November 1, 2026 and CAL_ on October 29, 2026.

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