Electronic Formulator vs iMark · Image Annotation Tool
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Electronic Formulator
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Electronic Engineer puts over 1,100 formulas and 24 reference tables in your pocket. No internet required. No ads. Just fast, accurate calculations when you need them. POWERFUL CALCULATORS Solve real-world electrical problems instantly: • Ohm's Law — Voltage, current, resistance, and power calculations • Voltage Divider — Output voltage, resistor values, current, and power dissipation • Three-Phase Power — Balanced systems, Wye and Delta connections • LED Circuits — Series resistor selection, power dissipation, max LEDs in series • 555 Timer — Astable and monostable modes with frequency, duty cycle, and timing • RLC Circuits — Resonant frequency, Q factor, bandwidth, impedance, and reactance • Power Triangle — Real, reactive, and apparent power with PF correction sizing • Impedance & Resistance — AC/DC circuit analysis • Star-Delta Conversion — Transform between Y and Δ configurations • Wheatstone Bridge — Unknown resistance and unbalanced bridge voltage • Inductors — Reactance, energy storage, series/parallel, and time constants • Wire Sizing — Circular mils, voltage drop (single and three-phase) • Capacitors, Transformers, Motors, Batteries, UPS, Lighting, and more PRO CALCULATORS Unlock advanced tools for professionals: • Op-Amp Circuits — Inverting, non-inverting, differential, and voltage follower • Filter Design — RC and RL low-pass, high-pass, and bandpass filters • PCB Trace Width — IPC-2221 current capacity and trace resistance • Skin Effect — Depth calculations for copper and custom conductors 24 REFERENCE TABLES Instantly look up critical data — no more flipping through handbooks: • AWG Wire Gauge — Diameter, area, resistance, and ampacity • NEC Ampacity Table — 60°C, 75°C, and 90°C conductor ratings • Resistor Color Codes — 4-band and 5-band decoding • Standard Resistor Values — E12, E24, E48, and E96 series • Circuit Breaker Sizes — Amp ratings, wire sizes, and typical applications • Wiring Color Codes — NEC, IEC, and Australian standards • Logic Gates Truth Tables — AND, OR, NAND, NOR, XOR, XNOR • Transformer Connections — Delta, Wye, Scott-T, Zig-Zag, and more • Power Factor Reference — Typical PF for motors, lighting, drives, and loads • SI Prefixes — From tera to femto with electronics examples • Conductor Properties — Resistivity, conductivity, and temp coefficients • Common Semiconductor Pinouts — BJTs, MOSFETs, regulators, 555, 741 • NEMA Enclosure Types — Indoor/outdoor ratings with IP equivalents • IP Protection Ratings — Solids and liquids protection levels • Ampacity Derating Factors — Temperature and conduit fill corrections • Standard Capacitor Values — Ceramic, film, and electrolytic • Cable Types — THHN, THWN, NM-B, MC, UF-B, and more • Decibel Reference — Power and voltage ratios at a glance • Motor Frame Sizes, Fuse Classes, Conduit Fill, and more UNIT CONVERSIONS Over 400 conversion formulas across 19 categories including metric, linear, liquid, cubic, pressure, weight, flow, BTU, horsepower, watts, joules, frequency, and HVAC. Plus 8 temperature scales: Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Delisle, Newton, and Rømer. BUILT FOR YOUR WORKFLOW • Favorites — Star the calculators you use daily for one-tap access • Calculation History — Every result saved automatically for easy reference • Export & Share — Send results to colleagues or save for documentation • Search & Filter — Find any formula or reference table in seconds • Dark Mode — Designed for comfortable use on job sites and in the field • US & Metric — Toggle between unit systems instantly WHY ELECTRONIC ENGINEER? Built by engineers, for engineers. We obsessed over accuracy, speed, and completeness so you can focus on what matters — getting the job done right. One purchase, no subscriptions, no recurring fees.
iMark · Image Annotation Tool
Enhance and annotate images with a comprehensive set of tools. Import from your photo library, camera, or maps, and customize your markups with various styles. Easily export and share your creations.
- Diverse annotation tools (arrow, text, mosaic, etc.)
- Import from photo library, camera, and maps
- Customizable color schemes and history sessions
- Crop and layer management
- Export with custom image size
- Supports iOS Photo Extension
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iMark is a simple & powerful image annotation tool. iMark supports various tools & styles. You could import photo from photo library, camera & map. · All Tools You Need: Arrow, Rect, Circle, Text, Magnifier, Mosaic, Pen, Spotlight · Create annotations from photo library, map or empty canvas · Easy Export: Export with custom image size. Share with your friends. · Customize: History sessions, custom color schemes, redo & undo action. · Advanced Feature: Crop & Layer Management · Supports iOS Photo Extension · Supports Home Screen 3D Touch Quick Action · Supports iPad Multitasking
Screenshots
Verdict
The clearest difference is update cadence: Electronic Formulator at every 9 days against iMark · Image Annotation Tool's every 2 months. iMark · Image Annotation Tool's advantage is iOS requirement (13.0 vs 26.2). 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. Electronic Formulator sells 1 one-off in-app purchase and iMark · Image Annotation Tool sells 4 one-off in-app purchases. Whichever you choose, the download price is not the number that matters.
Electronic Formulator ships an update every 9 days, iMark · Image Annotation Tool every 2 months. The most recent releases landed on October 8, 2026 and October 14, 2026 respectively.
| Parameter | Electronic Formulator | iMark · Image Annotation Tool |
|---|---|---|
| Price | Free | Free |
| Rating | — | 4.6 (381 ratings) — better |
| Positive reviews | — | 71.7% of reviews |
| Number of ratings | — | 381 — better |
| Update frequency | Every 9 days — better | Every 2 months |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | — | Free with in-app purchases |
| Devices | iPhone, iPad | iPhone, iPad, iPod — better |
| Requires iOS | 26.2 | 13.0 — better |
| Further details — not scored | ||
| Size | 19 MB | 93 MB |
| Age rating | 4+ | 4+ |
| Developer | Historycentral.com | iDaily Corp. |
Bugs and requests
Electronic Formulator
Not enough reviews yet to summarise bugs or requests.
iMark · Image Annotation Tool
Reported bugs
8 issues- App crashes when using brush/pen features
- Export button hidden by system UI
- Annotations disappearing after one day
- Keyboard engagement obscures image during text input
- Magnifier tool functionality issues
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- In-app review text not visible while typing
- Slow performance with multiple markups
- UI elements not accessible (white buttons on white background)
Requested features
18 requests- Ability to remove watermark (paid option requested)
- Multiple language support with easy switching
- Filled/solid geometric shapes
- Curved arrows instead of straight only
- Multiple font selection from Google Fonts
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- Text formatting (bold, italic, underline, strikethrough)
- Opacity/transparency control for colors
- Redaction/censoring tool for sensitive information
- Thinking bubbles with text capability
- Counter/numbering feature for annotations
- Copy/duplicate annotation elements
- Dark mode theme option
- Ability to import multiple images as layers
- Thinner line options for shapes and tools
- Rounded rectangle shape option
- Magnifier with square frame option
- Undo/redo history management
- Separate watermark and signature settings
In-app purchases
Electronic Formulator
- Electronic Pro$2.99
iMark · Image Annotation Tool
- Coffee$2.99
- Silver Coin$5.99
- Gold Coin$14.99
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- Coffee for Everyone$29.99
Questions
Is Electronic Formulator free?
Is iMark · Image Annotation Tool free?
Do Electronic Formulator or iMark · Image Annotation Tool have ads?
Which is updated more often, Electronic Formulator or iMark · Image Annotation Tool?
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