Comparison

ISO Fits vs Thread Calculator

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

Thread Calculator

This app provides a quick and easy way to calculate thread dimensions for various units, including tap hole sizes and bolt specifications. It helps metalworkers find precise measurements for internal and external threads without consulting tables.

Highlights
  • Thread cutting calculator for multiple units
  • Cold forming calculator
  • Thread repair calculator
  • Tap hole and bolt diameter calculation
  • Saves time compared to tables
Features
Read full description

The app includes: - A calculator for thread cutting for the following units: M, MF, UNC, UNEF, UNF, UNR, UNS, NPT, NPTF, NPSC, NPSF, NPSL, NPSM, BA, BSP, BSF, BSW, BSPP, TR, and TRF - A calculator for cold forming - A calculator for thread repair You want to know which tap hole you should drill for threading or which bolt you should use? With this app, you will find the desired measures in no time: Simply select the desired thread type, nominal size, and pitch and you will get the matching diameter for your project. This saves precious time you would have spent tediously searching for internal and external thread dimensions in tables. As this app is still in its development phase, new features will follow soon, so stay tuned! GSR Gustav Stursberg GmbH is a manufacturer for high-quality thread cutting tools with 130 years of operational experience in the area of threading tool production. The product portfolio includes a wide selection of tools for different areas of application. GSR taps, twist drills, round dies, and tool holders are manufactured to the highest quality standards in our own production facilities. The constant quality control during the production process guarantees a consistent good quality in all national as well as international production facilities. This requires enormous precision, which is reflected by our tools. Precision is in the details. Since 1889.

Screenshots

ISO Fits4 screens
Thread Calculator4 screens

Verdict

The call

ISO Fits and Thread Calculator both sit at 4.2 stars, but that hides the real split: 95% of ISO Fits's written reviews are positive against 33% of Thread Calculator's. ISO Fits also leads on ads (none vs shown) and update cadence (every 5 months vs every 18 months). Thread Calculator's advantage is in-app purchases (none vs 1). On price, rating, ratings volume 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. ISO Fits sells 1 one-off in-app purchase. Thread Calculator asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

On the App Store both sit at effectively the same score — 4.2 for ISO Fits against 4.3 for Thread Calculator. Both are backed by a comparable volume of ratings — 6 and 13 respectively. Written reviews are what separate them: 95% of ISO Fits's written reviews are positive against 33% of Thread Calculator's.

UpkeepUpdate frequency

ISO Fits ships an update every 5 months, Thread Calculator every 18 months. The most recent releases landed on September 12, 2026 and September 9, 2026 respectively.

Scorecard5 real differences · 5 level
ISO Fits versus Thread Calculator: the parameters behind the verdict, then further details
ParameterISO FitsThread Calculator
PriceFreeFree
Rating4.2 (6 ratings)4.3 (13 ratings) — better
Positive reviews94.6% of reviews — better33.3% of reviews
Number of ratings613 — better
Update frequencyEvery 5 months — betterEvery 18 months
AdsNo — betterYes
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesAd-supported — better
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.615.0 — better
Further details — not scored
Size66 MB25 MB
Age rating4+4+
DeveloperTrelleborg Sealing SolutionsGSR Gustav Stursberg GmbH

Customer experience

ISO Fits

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

Thread Calculator

All ratings13 ratings
Positive84.6%
Neutral7.7%
Negative7.7%
Written reviews3 reviews
Positive33.3%
Neutral0.0%
Negative66.7%

In-app purchases

1 purchases

ISO Fits

One-time1
  • Full Version with complete ISO286 Standard$1.99
None

Thread Calculator

No in-app purchases

Questions

Is ISO Fits free?
ISO Fits is free to download, with in-app purchases available.
Is Thread Calculator free?
Thread Calculator is free to download, with no in-app purchases.
Which has better reviews, ISO Fits or Thread Calculator?
Thread Calculator is rated higher. ISO Fits averages 4.2 out of 5 from 6 ratings, while Thread Calculator averages 4.3 from 13 ratings.
Do ISO Fits or Thread Calculator have ads?
Thread Calculator shows ads; ISO Fits does not.
Which is updated more often, ISO Fits or Thread Calculator?
ISO Fits ships an update every 5 months, and Thread Calculator every 18 months. Most recently, ISO Fits was updated on September 12, 2026 and Thread Calculator on September 9, 2026.

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