# Trace: Soap & Lye Calculator — Cold process recipes & cure > Cold process recipes & cure (iPhone/iPad app by Roman Kopaliani.) - Source: https://appshunter.io/ios/app/trace-soap-and-lye-calculator/id6778435536 (this page in markdown: same URL + `.md`) - Developer: [Roman Kopaliani](https://appshunter.io/developer/1635315269) - Category: Utilities, Lifestyle - Price: Free with in-app purchases - Age rating: 4+ - Requires: iOS 17.0 · 1 MB - Languages: American English, French (France), German (Germany), Italian, Brazilian Portuguese, European Spanish - Released: 2026-06-12 - Data updated: 2026-08-22 - User reviews in markdown: https://appshunter.io/ios/app/trace-soap-and-lye-calculator/id6778435536/reviews.md ## What is Trace? Free to use. The lye calculator and all six quality numbers are free forever — no account, no ads, no network, works fully offline. Trace Pro is an optional one-time purchase. Trace is a cold-process soap calculator with cited chemistry. Every quality bound, every additive limit, every fragrance cap names its source. FREE FOREVER • 31 oils with SAP values for NaOH (bar soap) and KOH (liquid soap), cross-checked against AOCS official methods and USDA Agricultural Handbook 8 • Dual-lye blends for cream soap and shaving soap • Three water expressions that interconvert cleanly: water % of oils, lye concentration %, water:lye ratio • Superfat / lye-discount slider • Citric acid auto-offsets the NaOH calculation (0.624 g NaOH per g citric acid, per Lovin' Soap Studio) • Sodium lactate, ROE and salt brine math with cited ranges • IFRA Category 9 (rinse-off toilet soap) fragrance caps for 20 common essential oils • All six soap qualities — hardness, cleansing, conditioning, bubbly lather, creamy lather, longevity — computed from weighted-average fatty-acid composition, each shown with the range its source publishes • Adjustable lye purity for NaOH (default 99%) and KOH (default 90%) • Every cited source listed in one Sources screen THE WEDGE Most soap calculators surface "soap qualities" as opaque numbers. Trace shows the same numbers, free — but on every bound, tap to see exactly which named source backs it. Hardness 29–54: per Kevin Dunn, Scientific Soapmaking (Hampden-Sydney College, 2010). Citric acid 0.624× extra NaOH: per Lovin' Soap Studio. IFRA Cat 9 fragrance caps: per the IFRA Standards 51st Amendment (2025). TRACE PRO — OPTIONAL, ONE-TIME Try Pro free for 7 days of actual use — days you don't open Trace don't count against it. After that Pro is a single purchase. No subscription, ever. • Cost per bar — price your oils once and Trace costs every batch: oils, lye and fragrance totalled, then divided by your bar weight. The one thing a free web calculator cannot do, because it never knows what you paid. • Save & reopen recipes — keep every recipe you calculate • Multi-batch cure tracker — log every batch from mix to cured: gel check, unmold, zap test, pH test • Brand-aware oil-supplier presets: Bramble Berry, Soaper's Choice, Bulk Apothecary, Essential Depot, Wholesale Supplies Plus, plus Costco / Trader Joe's / Spectrum generics SOURCES Kevin Dunn (Scientific Soapmaking), AOCS, USDA Handbook 8, Susan Miller Cavitch (The Soapmaker's Companion), Anne L. Watson (Smart Soapmaking), Modern Soapmaking (Kenna Cote), Lovin' Soap Studio (Amanda Gail Aaron), IFRA Standards, Handcrafted Soap & Cosmetic Guild. THE MOON DOG PROMISE • No subscription. No ads. No account, no login, no signup, no network. • Works fully offline. No data collection. DISCLAIMER Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are corrosive and can cause serious burns or eye damage. Always follow your supplier's Material Safety Data Sheet (MSDS) and the safety practices recommended by the Handcrafted Soap & Cosmetic Guild (HSCG). Trace cites named sources but does not generate recipes — independent verification against your supplier's specifications is your responsibility. © 2026 Roman Kopaliani ## Pricing and in-app purchases Base price: Free. **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | Trace Pro (lifetime) | $2.99 | one-time | ## Version history (last 5 releases) ### 1.8 — 2026-08-18 • All six soap qualities — hardness, cleansing, conditioning, bubbly, creamy, longevity — are now free forever. They were behind Pro; they shouldn't have been. • New in Pro: cost per bar. Price your oils once and Trace costs every batch, then divides by your bar weight. • The paywall, the trial banner and the upgrade screens are now translated — they were English-only in every language. ### 1.7 — 2026-08-15 • The free trial now runs for 7 days of actual use — days you don't open Trace don't count against it • Everyone gets a fresh 7-day trial with this update, so you can pick up where you left off • Trial time remaining is now shown in days ### 1.6 — 2026-07-24 • Corrected citric acid lye adjustment to the stoichiometric 0.624 g NaOH (0.876 g KOH) per gram of citric acid — if you use citric acid, please recalculate saved recipes • Liquid-soap (KOH) recipes with citric acid now adjust KOH, not NaOH • Ounce display now works everywhere • Water input resets to a sensible default when switching modes • Trial countdown shown; cure length adjustable per batch ### 1.5 — 2026-07-23 Behind-the-scenes improvements for a smoother, faster app. ### 1.4 — 2026-07-16 The number keyboard now has a Done button, so you can dismiss it when you're finished. Thanks to everyone who wrote in about this. ## Apps similar to Trace | App | Rating | Price | Category | | --- | --- | --- | --- | | [Simple SoapCalc – Soap Calc](https://appshunter.io/ios/app/simple-soapcalc-soap-calc/id6756240234) | 4.7 (11) | Free | Utilities | | [SoapCraft: Soap Calculator](https://appshunter.io/ios/app/soapcraft-soap-calculator/id6772685450) | — | Free | Utilities | | [Soap Maker: Recipes & Calculs](https://appshunter.io/ios/app/soap-maker-recipes-and-calculs/id6770494038) | — | Free | Utilities | | [Lye & Loaf: Soap Calculator](https://appshunter.io/ios/app/lye-and-loaf-soap-calculator/id6780806049) | — | Free | Utilities | | [BeePerf](https://appshunter.io/ios/app/beeperf/id1531124152) | — | Free | Utilities | | [Les P’t**s Api](https://appshunter.io/ios/app/les-pts-api/id1597456287) | — | Free | Utilities | ## More apps by Roman Kopaliani - [Soak: Hot Tub & Spa Calc](https://appshunter.io/ios/app/soak-hot-tub-and-spa-calc/id6775030424) - [Frost: Cold Plunge Care](https://appshunter.io/ios/app/frost-cold-plunge-care/id6776702484) - [Reef: Aquarium Chemistry Calc](https://appshunter.io/ios/app/reef-aquarium-chemistry-calc/id6776750986) - [Pond: Koi Chemistry](https://appshunter.io/ios/app/pond-koi-chemistry/id6777459595) - [Watt: Solar for Van & RV](https://appshunter.io/ios/app/watt-solar-for-van-and-rv/id6777471058) - [Saline: Saltwater Pool Calc](https://appshunter.io/ios/app/saline-saltwater-pool-calc/id6777715538) All apps by Roman Kopaliani: https://appshunter.io/developer/1635315269 ## Related topics [soap lye calculator](https://appshunter.io/ios/topics/soap-lye-calculator) · [tallowe](https://appshunter.io/ios/topics/tallowe) --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-22.*