Interpolator vs Tanker
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Interpolator
Easily find values within tables using interpolation for two or three rows. This utility app simplifies calculations without needing a separate calculator, making it ideal for various table-based environments.
- Two-row interpolation
- Three-row interpolation
- Table value lookup
- No calculator needed
- Cargo surveyor tool
- General table use
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This is a small app which makes it very easy to look up values in tables (math etc) when you have to interpolate both in two and in three rows. No more need for a calculator to interpolate manually. This app was designed primarily for cargo surveyors working with tank calibration tables, but the app does have its application in any environment where tables are used. As of 13th January 2015, this app has become FREE until further notice.
Tanker
This app streamlines the process of calculating marine fuel tank volumes. It eliminates the need for physical sounding tables and manual calculations, providing instant volume lookups with trim corrections automatically applied. Users can manage target fill levels, track fuel transfers, and share tables with their fleet.
- Instant volume lookups
- Target fill level setting
- CSV import and tank duplication
- Unit conversion and safe fill percentages
- Bunkering mode for real-time tracking
- Offline functionality
- Cloud sharing via TankerBase
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Tanker - Marine Fuel Tank Calculator Stop thumbing through dirty sounding table binders. Get instant tank volumes. Every chief engineer knows the routine: sound the tanks, walk back to the control room, dig out the crusty binder, flip through pages for each tank, look up trim corrections, punch numbers into a calculator. Tanker cuts this 20-minute process down to 2 minutes. The Old Way vs. The Tanker Way Old: Drop tape → Record height → Walk to control room → Find binder → Flip pages → Look up trim → Find volume → Repeat for each tank → Add on calculator Tanker: Drop tape → Tap tank → Enter sounding → Get instant volume → Done How It Works Build your vessel's sounding tables once using CSV import, the Express Editor, or by duplicating similar tanks. Select your vessel, tap a tank, enter your sounding—instant volume lookup with trim automatically applied. Sound all your tanks, hit the equals button, get your total. Features That Save Time - Instant Volume Lookups - No more flipping through binder pages - Target Fill Levels - Set specific fill preferences per tank to maintain vessel stability - Multiple Build Methods - CSV import, Express Editor, tank duplication - Smart Tools Built In - Unit conversion, safe fill percentages, sounding history with trends - Bunkering Mode - Track fuel transfers in real-time with target level warnings - Works Offline - All calculations on-device, no internet needed - Share Tables - AirDrop to crew or publish to TankerBase for the whole fleet Maintain Stability During Transfers Set target fill levels for each tank based on your vessel's stability requirements. During bunkering, Tanker warns you when approaching target levels—keeping your vessel balanced without mental math or paper notes. TankerBase: Cloud Sharing Create an account to share your sounding tables online. Share peer-to-peer with your relief engineer or publish your tables to our database for anyone to subscribe to. Build once, share with your entire fleet. Built by Engineers, For Engineers Tanker was created by a chief engineer who got tired of the sounding table binder routine. If you've ever stood in an engine room covered in fuel oil trying to find the right page in a beat-up binder, this app is for you. Download Tanker and leave the binder in the drawer. Subscription Details Yearly Plan: $19.99/year Lifetime Plan: $59.99 (best value) Payment is charged to your Apple Account at confirmation of purchase. Subscriptions automatically renew unless canceled at least 24 hours before renewal. Manage or cancel anytime in your App Store account settings. Subscription Terms: https://www.seasmith.net/tanker-subscription-terms/ Privacy Policy: https://www.seasmith.net/tanker-privacy Terms of Use: https://www.seasmith.net/tanker-terms
Screenshots
Verdict
The clearest difference is in-app purchases: Interpolator at none against Tanker's 2. Interpolator also leads on ratings volume (75 vs 1) and iOS requirement (12.0 vs 27.0). Tanker's advantage is update cadence (monthly vs every 4 months). On price, rating, 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
Both are free to download. Tanker sells 2 one-off in-app purchases. Interpolator asks for nothing beyond the download.
On the App Store both sit at effectively the same score — 4.9 for Interpolator against 5.0 for Tanker. That said, the two scores are not equally well evidenced: Interpolator has 75 ratings behind it against 1, so its average is the more settled of the two.
Interpolator ships an update every 4 months, Tanker monthly. The most recent releases landed on November 9, 2026 and November 2, 2026 respectively.
| Parameter | Interpolator | Tanker |
|---|---|---|
| Price | Free | Free |
| Rating | 4.9 (75 ratings) | 5.0 (1 ratings) — better |
| Positive reviews | 66.7% of reviews | — |
| Number of ratings | 75 — better | 1 |
| Update frequency | Every 4 months | Monthly — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Free — better | Free with in-app purchases |
| Devices | iPhone, iPod | iPhone, iPad |
| Requires iOS | 12.0 — better | 27.0 |
| Further details — not scored | ||
| Size | 18 MB | 20 MB |
| Age rating | 4+ | 4+ |
| Developer | ron mooring | Pearson Smith |
Customer experience
Interpolator
Tanker
In-app purchases
Interpolator
No in-app purchases
Tanker
- Full Version$4.99
- Tanker Pro Lifetime$59.99









