Comparison

ISO Fits vs Hydraulic Engineer

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

Head to head
About

ISO Fits

Calculate ISO fits and tolerances for shafts and bores. Supports metric and inch units, displays detailed fit definitions, and includes visual charts and educational videos.

Highlights
  • ISO fits calculation
  • Tolerance class display
  • Metric/inch unit switching
  • Tolerance charts
  • Updated YouTube videos
Features
Read full description

It includes the following features: - Fits calculation: Upon entering the nominal diameter (of either bore or shaft), users select their tolerance classes for bore and shaft. The app then provides the complete ISO fits definition with all relevant values. - Tolerances: Shows the tolerances for the most commonly used ISO tolerance classes. - switch between metric and inch version. - Charts: Shows the most common ISO tolerances classes in a diagram. - Videos: Features the automatically updated latest TSS youtube videos. The results of this application are based on DIN ISO 286 Nominal dimension: 1-3150mm following tolerances included: Shaft: a9, a10, a11, a12, a13, b8, b9, b10, b11, b12, b13, c8, c9, c10, c11, c12, cd5, cd6, cd7, cd8, cd9, cd10, d5, d6, d7, d8, d9, d10, d11, d12, d13, e5, e6, e7, e8, e9, e10, ef3, ef4, ef5, ef6, ef7, ef8, ef9, ef10, f3, f4, f5, f6, f7, f8, f9, f10, fg3, fg4, fg5, fg6, fg7, fg8, fg9, fg10, g3, g4, g5, g6, g7, g8, g9, g10, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11, h12, h13, h14, h15, h16, h17, h18, js1, js2, js3, js4, js5, js6, js7, js8, js9, js10, js11, js12, js13, js14, js15, js16, js17, js18, j5, j6, j7, j8, k3, k4, k5, k6, k7, k8, k9, k10, k11, k12, k13, m3, m4, m5, m6, m7, m8, m9, n3, n4, n5, n6, n7, n8, n9, p3, p4, p5, p6, p7, p8, p9, p10, r3, r4, r5, r6, r7, r8, r9, r10, s3, s4, s5, s6, s7, s8, s9, s10, t5, t6, t7, t8, u5, u6, u7, u8, u9, v5, v6, v7, v8, x5, x6, x7, x8, x9, x10, y6, y7, y8, y9, y10, z6, z7, z8, z9, z10, z11, za6, za7, za8, za9, za10, za11, zb7, zb8, zb9, zb10, zb11, zc7, zc8, zc9, zc10, zc11 Bore: A9, A10, A11, A12, A13, B8, B9, B10, B11, B12, B13, C8, C9, C10, C11, C12, C13, CD6, CD7, CD8, CD9, CD10, D6, D7, D8, D9, D10, D11, D12, D13, E5, E6, E7, E8, E9, E10, EF3, EF4, EF5, EF6, EF7, EF8, EF9, EF10, F3, F4, F5, F6, F7, F8, F9, F10, FG3, FG4, FG5, FG6, FG7, FG8, FG9, FG10, G3, G4, G5, G6, G7, G8, G9, G10, H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15, H16, H17, H18, JS1, JS2, JS3, JS4, JS5, JS6, JS7, JS8, JS9, JS10, JS11, JS12, JS13, JS14, JS15, JS16, JS17, JS18, J6, J7, J8, J9, K3, K4, K5, K6, K7, K8, K9, K10, M3, M4, M5, M6, M7, M8, M9, M10, N3, N4, N5, N6, N7, N8, N9, N10, N11, P3, P4, P5, P6, P7, P8, P9, P10, R3, R4, R5, R6, R7, R8, R9, R10, S3, S4, S5, S6, S7, S8, S9, S10, T5, T6, T7, T8, U5, U6, U7, U8, U9, U10, V5, V6, V7, V8, X5, X6, X7, X8, X9, X10, Y6, Y7, Y8, Y9, Y10, Z6, Z7, Z8, Z9, Z10, Z11, ZA6, ZA7, ZA8, ZA9, ZA10, ZA11, ZB7, ZB8, ZB9, ZB10, ZB11, ZC7, ZC8, ZC9, ZC10, ZC11

About

Hydraulic Engineer

This comprehensive calculator app offers over 1,000 hydraulic engineering formulas across 13 categories. It includes temperature conversions, reference tables, and the ability to save and share calculations. Works offline and supports both US Customary and SI Metric units.

Highlights
  • Over 1,000 hydraulic formulas
  • 13 specialized calculator categories
  • Temperature scale converters
  • Professional reference tables
  • Save and share calculations
  • Works offline
  • US Customary and SI Metric units
Features
Read full description

HYDRAULIC ENGINEER is the most comprehensive hydraulic engineering calculator available on the App Store, featuring over 1,000 formulas across 13 specialized calculator categories, 8 temperature scale converters, and 8 professional reference tables. CALCULATOR CATEGORIES - Actuator Formulas — cylinder force, stroke, speed, and rod calculations - Fluid Power — pressure, flow, horsepower, and torque calculations - Pump Laws — affinity laws for speed, flow, pressure, and power - Vehicle Drive — drive speed, tractive effort, gradeability, and drawbar pull - Hydraulic Tubing — wall thickness, burst pressure, and working pressure - Cylinder Calculations — extend/retract speed, rod end area, and cycle times - Thermal Hydraulics — heat generation, reservoir cooling, heat exchangers, and energy to heat fluid - Oil Velocity & Pressure Loss — pipe velocity, pressure drop per foot, and total system losses - Pipe Flow — Reynolds number, Darcy-Weisbach head loss, laminar friction, and orifice flow - Accumulator Sizing — discharge volume, precharge pressure, adiabatic and isothermal gas volumes - Reservoir Sizing — open/closed circuit sizing, cylinder-based sizing, and oil weight calculations - AC/DC Electrical — Ohm's law, power, resistance, inductance, and motor selection - Area Formulas — 60 geometric area calculations for every common shape 700+ CONVERSION FORMULAS Pressure, horsepower, BTU, flow rates, linear measure, square measure, cubic measure, liquid measure, weights, watts, power, HVAC, metric, sand-to-volume, and fraction conversions. 8 TEMPERATURE SCALES Convert between Celsius, Fahrenheit, Kelvin, Rankine, Reaumur, Newton, Delisle, and Romer — 56 conversion formulas covering every combination. 8 PROFESSIONAL REFERENCE TABLES - Pipe Schedule (Schedule 40 & 80) - ISO Viscosity Grades - Recommended Flow Velocities - Hydraulic Hose Sizing (SAE) - JIC Thread Sizes - Pipe Roughness Values - O-Ring Sizes (AS568) - Wire Rope Working Load Limits KEY FEATURES - Save and share any calculation result - Share reference tables - Calculation history - Favorites for quick access to your most-used formulas - Switch between US Customary and SI Metric units - Dual-unit display shows both US and metric values simultaneously - Dark mode optimized interface - Works offline — no internet connection required PREMIUM UPGRADE Unlock sharing, advanced calculator sections, and unlimited history with a one-time lifetime purchase — no subscriptions. HYDRAULIC ENGINEER is designed for working hydraulic engineers, technicians, maintenance professionals, and engineering students. If there are formulas or reference tables you'd like to see added, just use the built-in feedback feature to let us know.

Screenshots

ISO Fits4 screens
Hydraulic Engineer4 screens

Verdict

The call

The clearest difference is review sentiment: ISO Fits at 95% against Hydraulic Engineer's 25%. ISO Fits also leads on price (Free vs $4.99) and rating (4.2 vs 4.0). On update cadence, 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

CostPrice · In-app purchases · Ads · Monetization

ISO Fits is free to download; Hydraulic Engineer costs $4.99 up front. ISO Fits sells 1 one-off in-app purchase and Hydraulic Engineer sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

ReceptionRating · Positive reviews · Number of ratings

ISO Fits holds the better App Store score, 4.2 against 4.0. That said, the two scores are not equally well evidenced: ISO Fits has 6 ratings behind it against 1, so its average is the more settled of the two. Written reviews point the same way: 95% of ISO Fits's written reviews are positive against 25% of Hydraulic Engineer's.

UpkeepUpdate frequency

ISO Fits ships an update every 5 months, Hydraulic Engineer every 6 months. The most recent releases landed on September 12, 2026 and September 26, 2026 respectively.

Scorecard6 real differences · 4 level
ISO Fits versus Hydraulic Engineer: the parameters behind the verdict, then further details
ParameterISO FitsHydraulic Engineer
PriceFree — better$4.99
Rating4.2 (6 ratings) — better4.0 (1 ratings)
Positive reviews94.6% of reviews — better25.0% of reviews
Number of ratings6 — better1
Update frequencyEvery 5 months — betterEvery 6 months
AdsNoNo
In-app purchasesYesYes
MonetizationFree with in-app purchases — betterPaid
DevicesiPhone, iPad, iPod — betteriPhone, iPad
Requires iOS15.6 — better18.6
Further details — not scored
Size66 MB19 MB
Age rating4+4+
DeveloperTrelleborg Sealing SolutionsHistorycentral.com

Customer experience

ISO Fits

All ratings6 ratings
Positive83.3%
Neutral0.0%
Negative16.7%
Written reviews37 reviews
Positive94.6%
Neutral0.0%
Negative5.4%

Hydraulic Engineer

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews8 reviews
Positive25.0%
Neutral25.0%
Negative50.0%

In-app purchases

1 purchases

ISO Fits

One-time1
  • Full Version with complete ISO286 Standard$1.99
1 purchases

Hydraulic Engineer

One-time1
  • Hydraulic Pro$3.99

Questions

Is ISO Fits free?
ISO Fits is free to download, with in-app purchases available.
Is Hydraulic Engineer free?
Hydraulic Engineer costs $4.99, and also offers in-app purchases.
Which has better reviews, ISO Fits or Hydraulic Engineer?
ISO Fits is rated higher. ISO Fits averages 4.2 out of 5 from 6 ratings, while Hydraulic Engineer averages 4.0 from 1 ratings.
Do ISO Fits or Hydraulic Engineer have ads?
Neither ISO Fits nor Hydraulic Engineer shows ads.
Which is updated more often, ISO Fits or Hydraulic Engineer?
ISO Fits ships an update every 5 months, and Hydraulic Engineer every 6 months. Most recently, ISO Fits was updated on September 12, 2026 and Hydraulic Engineer on September 26, 2026.

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