Comparison

Vibra Calc vs PrepFE

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

Head to head
About

Vibra Calc

This app calculates vibration frequencies for various rotating machinery components and includes an interactive vibration severity test tool. It also offers a calculator for converting vibration units and a glossary of terms.

Highlights
  • Induction motor frequency calculation
  • Detailed gear frequencies
  • Rolling element bearing frequencies
  • Pump and fan vane pass frequencies
  • Journal bearing frequencies
  • Interactive vibration severity test
  • Vibration unit conversion
Features
Read full description

Vibra Calc calculates vibration frequencies of rotating machinery components given the specifications of each component. It includes induction motors, gears, rolling element bearings, pumps, fans & blowers, journal bearings, and belts & pulleys. Also, it provides an interactive vibration severity test tool based on the ISO 10816-3 standard. Furthermore, Vibra Calc has a calculator for vibration conversions from/to displacement, velocity, and acceleration with metric and imperial units. Features: - Induction Motor Frequency Calculator - Full detailed gears frequencies (main, harmonics, sidebands) up to 4X - Rolling element frequencies (BPFI, BPFO, BSF, FTF) given the bearing dimension or the bearing model number - Pump vane pass frequencies up to 4X - Fans blade pass frequencies up to 4X - Journal bearing frequencies corresponding to wear and oil whirl phenomena presented in a table and over an interactive chart - Belt frequencies up to 4X - Interactive Vibration Severity Test Tool based on ISO 10816-3 (INPUTS: vibration velocity in mm/s or inch/s, type of support, type of machine & OUTPUTS: Machine Operation Condition) - E-mail and Save the screen option for vibration severity tool - Vibration calculator to convert displacement/velocity/accelerations to each other (Metric & Imperial) - Vibration Glossary - Metric and Imperial units provided for all input dimensions DISCLAIMER: Vibra Calc is intended for educational purposes. Although the calculations by this app were made with great care, it may contain error or inaccuracies. Using the results of the calculations is the responsibility of the user.

About

PrepFE

Prepare for the FE Mechanical exam with practice problems and flashcards. Learn by doing with expert-curated content, track your progress, and identify areas for improvement. Study conveniently on your mobile device, anytime, anywhere.

Highlights
  • Practice FE exam questions
  • Interactive practice exams
  • Hundreds of practice questions
  • Detailed step-by-step explanations
  • Reinforce learning with flashcards
  • Breakdown of strengths and weaknesses
Features
Read full description

Don't spend time relearning topics from scratch and using poor resources. Jump right into practice problems and learn by doing! Supplement your learning with flash cards to learn the FE Reference Handbook and be familiar with your discipline's concepts. Take your exam practice on the go and learn with our curated content by engineering experts. Study whenever and wherever it’s convenient with PrepFE™. No need to carry around books and study guides. All you need is your phone and determination. Start your Professional Engineer journey and download the PrepFE - Mechanical app. Install the free version today and jump start your studying! We have provided a limited free version of the app that you can try before deciding to upgrade. This version includes a limited set of practice questions, flash cards, and basic progress metrics. *Practice FE exam questions* *Interactive Practice Exams* *Hundreds of Practice Questions* *Detailed & Step-by-Step Explanations* *Reinforce learning with Flash Cards* *Breakdown of strengths and weaknesses* *Updated for 2020* We have up to date content for the new category specifications: • Mathematics • Probability and Statistics • Ethics and Professional Practice • Engineering Economics • Electricity and Magnetism • Statics • Dynamics, Kinematics, and Vibrations • Mechanics of Materials • Material Properties and Processing • Fluid Mechanics • Thermodynamics • Heat Transfer • Measurements, Instrumentation, and Controls • Mechanical Design and Analysis

Screenshots

Vibra Calc4 screens
PrepFE4 screens

Verdict

The call

The clearest difference is rating: Vibra Calc at 4.0 against PrepFE's 2.0. Vibra Calc also leads on in-app purchases (none vs 9) and review sentiment (50% vs 17%). PrepFE's advantage is update cadence (every 2 months vs every 39 months) and ratings volume (57 vs 2). On price, ads 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. PrepFE sells 6 one-off in-app purchases. Vibra Calc asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Vibra Calc holds the better App Store score, 4.0 against 2.0. That said, the two scores are not equally well evidenced: PrepFE has 57 ratings behind it against 2, so its average is the more settled of the two. Written reviews point the same way: 50% of Vibra Calc's written reviews are positive against 17% of PrepFE's.

UpkeepUpdate frequency

Vibra Calc ships an update every 39 months, PrepFE every 2 months. The most recent releases landed on October 14, 2026 and October 8, 2026 respectively.

Scorecard7 real differences · 3 level
Vibra Calc versus PrepFE: the parameters behind the verdict, then further details
ParameterVibra CalcPrepFE
PriceFreeFree
Rating4.0 (2 ratings) — better2.0 (57 ratings)
Positive reviews50.0% of reviews — better16.7% of reviews
Number of ratings257 — better
Update frequencyEvery 39 monthsEvery 2 months — better
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS8.0 — better13.0
Further details — not scored
Size22 MB288 MB
Age rating4+4+
DeveloperMotionics LLCPrepFE, Inc.

Customer experience

Vibra Calc

All ratings2 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews2 reviews
Positive50.0%
Neutral0.0%
Negative50.0%

PrepFE

All ratings57 ratings
Positive24.6%
Neutral0.0%
Negative75.4%
Written reviews42 reviews
Positive16.7%
Neutral0.0%
Negative83.3%

In-app purchases

None

Vibra Calc

No in-app purchases

6 purchases

PrepFE

One-time6
  • 1 Month Access Renewal$47.99
  • 1 Month Access2 variants$59.99
  • 3 Months Access Renewal$61.99
Show 3 more
  • 6 Months Access Renewal$75.99
  • 3 Months Access2 variants$79.99
  • 6 Months Access2 variants$99.99

Questions

Is Vibra Calc free?
Vibra Calc is free to download, with no in-app purchases.
Is PrepFE free?
PrepFE is free to download, with in-app purchases available.
Which has better reviews, Vibra Calc or PrepFE?
Vibra Calc is rated higher. Vibra Calc averages 4.0 out of 5 from 2 ratings, while PrepFE averages 2.0 from 57 ratings.
Do Vibra Calc or PrepFE have ads?
Neither Vibra Calc nor PrepFE shows ads.
Which is updated more often, Vibra Calc or PrepFE?
Vibra Calc ships an update every 39 months, and PrepFE every 2 months. Most recently, Vibra Calc was updated on October 14, 2026 and PrepFE on October 8, 2026.

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