Rupee Finance Toolkit — Calculator App

A complete, offline-first Android finance calculator app built specifically for the Indian market. Covers EMI, GST, salary breakdowns, income tax (FY 2024-25), SIP, compound interest, NPV/IRR, discount, ROI, and more — all in Indian Rupee format (lakh/crore) with correct Indian tax rules, EPF, CGST/SGST/IGST splits, and Section 87A rebate. Clean Material Design UI, no ads, no internet required, and ready to publish on Google Play, Amazon App Store, or any Android platform.

Rupee Finance Toolkit is a production-ready Android app source code (Kotlin + Jetpack) designed from the ground up for Indian users. India has a unique financial landscape — lakh/crore number formatting, GST with CGST/SGST/IGST splits, EPF at 12% of basic salary, professional tax varying by state, and income tax rules that change every budget. Generic finance apps get these wrong. This app gets them right.

Every calculator is self-contained with its own activity, formula reference, worked examples, FAQs, and real-life use cases — so end users understand their finances, not just the answer. The codebase is modular and clean, making it straightforward to add new calculators, rebrand, or integrate ads.

Whether you’re building a product for salaried professionals who want to understand their take-home pay, small business owners who need GST breakdowns, or investors planning SIPs — this source code gives you a complete, tested, India-specific financial calculator that is ready to ship.

All amounts display in Indian format (₹1,00,000 not ₹100,000). All tax rules are updated for FY 2024-25 including the revised new regime slabs, standard deduction of ₹75,000, and Section 87A rebate for income up to ₹7 lakh. Professional tax defaults are correct for Maharashtra, Karnataka, West Bengal, Tamil Nadu, and Gujarat, with a note for zero-PT states like Delhi and UP.

CALCULATORS INCLUDED

1. EMI / Loan Calculator — Reducing-balance EMI formula: P × r × (1+r)^{n / ((1+r)}n − 1) — Inputs: Principal, annual interest rate, tenure in months — Outputs: Monthly EMI, total interest payable, total amount payable — Covers home loans, car loans, personal loans, education loans

2. GST Calculator — All 5 Indian GST slabs: 0%, 5%, 12%, 18%, 28% — GST-exclusive (add GST to base) and GST-inclusive (extract GST from total) modes — Automatic CGST/SGST split for intra-state and IGST for inter-state supply — GST registration threshold info (₹40 lakh goods / ₹20 lakh services)

3. Salary / CTC Calculator — User-editable Basic Salary % (not hardcoded — pulled from payslip) — Employee PF deduction at configurable rate (default 12% of basic) — Professional tax input (state-specific, defaults to ₹200/month) — TDS / income tax monthly deduction input — Outputs: Gross monthly, net take-home, weekly, daily (250 working days), hourly

4. Income Tax Estimator (FY 2024-25 New Regime) — Correct tax slabs: 0% up to ₹3L, 5% ₹3–7L, 10% ₹7–10L, 15% ₹10–12L, 20% ₹12–15L, 30% above ₹15L — Standard deduction of ₹75,000 automatically applied — Section 87A rebate: zero tax if net taxable income ≤ ₹7 lakh — Surcharge and cess calculation included

5. Simple Interest Calculator — Formula: SI = P × R × T / 100 — Total amount and interest breakdown

6. Compound Interest Calculator — Formula: A = P × (1 + r/n)^{(n×t) — Configurable compounding frequency: annual, half-yearly, quarterly, monthly}

7. SIP / Investment Planner — Future value with monthly contributions — Formula: FV = PV × (1+r)n + PMT × ((1+r)^n − 1) / r — Ideal for mutual fund SIP planning

8. Discount Calculator — Discount amount and final discounted price — Useful for retail and e-commerce pricing

9. Profit / Margin Calculator — Gross profit margin, net profit, ROI — Revenue and COGS inputs

10. NPV / IRR Calculator — Net Present Value with configurable discount rate and multiple cash flows — IRR using bisection method with 1000-iteration convergence

11. Payback Period Calculator — Initial investment vs annual cash inflow ratio

12. Inflation Calculator — Inflation-adjusted future value — Real purchasing power (present value after inflation)

13. Currency Converter — Converts between currencies using user-supplied exchange rates — Useful for import/export businesses and NRI users

TECHNICAL FEATURES

— Language: Kotlin — Architecture: Activity-based with BaseCalculatorActivity for shared logic — UI: Material Design with custom drawables, CardView, LinearLayout — Number formatting: DecimalFormatSymbols with Locale(“en”, “IN”) for correct lakh/crore grouping — MathUtils: Centralized utility class for all financial formulas — easy to extend — UIUtils: Input validation, clipboard copy, toast helpers — Each calculator has its own Activity with self-contained educational content (formula, examples, FAQs, tips) — No external dependencies beyond AndroidX and Material Design library — Fully offline — no API calls, no backend, no login — minSdkVersion: 21 (Android 5.0+), targetSdkVersion: 34 — Compatible with Google Play, Amazon App Store, and sideload APK distribution

DEVELOPMENT ENVIRONMENT — Android Studio Hedgehog (2023.1.1) or later — JDK 17 or later — Gradle 8.x (wrapper included in project) — Kotlin 1.9+

DEVICE / EMULATOR REQUIREMENTS — Android 5.0 (API 21) minimum — Android 14 (API 34) target SDK — Any screen size from 5” to 12” tablets — UI is fully responsive

DEPENDENCIES (all declared in build.gradle) — androidx.core:core-ktx — androidx.appcompat:appcompat — com.google.android.material:material — androidx.cardview:cardview — androidx.constraintlayout:constraintlayout

NO EXTERNAL SERVICES REQUIRED — No Firebase, no analytics SDK, no ad SDK (AdMob integration is straightforward to add if needed) — No internet permission required — No API keys needed

SIGNING AND PUBLISHING — Generate a release keystore using Android Studio or keytool — Configure signingConfigs in build.gradle with your keystore details — Build a release APK or AAB for upload to Google Play or Amazon App Store

STEP 1 — DOWNLOAD AND EXTRACT Download the ZIP from CodeCanyon. Extract to a folder of your choice. Do not extract to a path with spaces or special characters (e.g., avoid “My Documents”).

STEP 2 — OPEN IN ANDROID STUDIO Open Android Studio → File → Open → select the extracted “FinanceCalculators” folder (the one containing the top-level build.gradle). Wait for Gradle sync to complete. If sync fails, go to File → Invalidate Caches / Restart.

STEP 3 — CHANGE PACKAGE NAME (for publishing) In Android Studio: Right-click the package “com.aclabs.rftoolkit” in the Project view → Refactor → Rename. Update applicationId in app/build.gradle to your new package name. Update the package attribute in AndroidManifest.xml.

STEP 4 — UPDATE APP NAME AND BRANDING Open res/values/strings.xml. Change app_name to your desired app name. Replace the launcher icon files in res/mipmap-* folders with your own icons (use Android Studio’s Image Asset Studio: right-click res → New → Image Asset).

STEP 5 — CUSTOMIZE THEME / COLORS Open res/values/colors.xml and res/values/themes.xml. Change the primary color, accent color, and status bar color to match your brand.

STEP 6 — ADD OR REMOVE CALCULATORS (OPTIONAL) Each calculator is a separate Activity class. To add a new calculator: copy an existing Activity as a template, add a new entry in the main menu RecyclerView adapter, and register the Activity in AndroidManifest.xml. To remove a calculator: delete its Activity file and remove it from the menu.

STEP 7 — BUILD DEBUG APK (TESTING) In Android Studio: Build → Build Bundle(s) / APK → Build APK . Install on a connected device or emulator via Run → Run ‘app’.

STEP 8 — BUILD RELEASE APK / AAB (PUBLISHING) Generate a keystore: Build → Generate Signed Bundle / APK. Select APK or Android App Bundle (AAB recommended for Play Store). Fill in keystore details, select release build variant, and build. The signed output will be in app/release/.

STEP 9 — PUBLISH TO GOOGLE PLAY Create a developer account at play.google.com/console. Create a new app, fill in store listing details (use the descriptions provided with this purchase). Upload the AAB under Production or start with Internal Testing. Complete content rating questionnaire — select “Finance” category. Submit for review.

STEP 10 — PUBLISH TO AMAZON APP STORE (OPTIONAL) Log in to developer.amazon.com. Create a new Android app submission. Upload the APK (Amazon does not support AAB directly — build a signed APK instead). Fill in app description and screenshots. Submit for approval (usually 1–3 business days).

APK: https://www.mediafire.com/file/e49w0wuf5eh736l/RupeeFinanceToolkitAV.apk/file