10B Calc Support & Diagnostics

Fastest diagnostic route: Inside the 10B Calc app on your iPhone, iPad, or Mac, open the calculation you are working on, then tap Settings → Contact the developer. The exact inputs, compounding frequency, and period mode are cleanly formatted as text, enabling us to reproduce your calculation down to the fractional cent.

My answer doesn't match my lender's or my textbook

1. Payments per year (P/YR). Standard consumer auto and mortgage loans in most countries use 12 payments per year. However, university finance courses, Canadian mortgages, and government bond problems often specify 1 (annual) or 2 (semi-annual). This setting is displayed right next to your answer register on 10B Calc.
2. Start or End of period (Payment Timing). Term loans and mortgages are normally paid in arrears at the End of the period. Leases, insurance policies, and advance rent are paid at the Start of the period. For instance, a $25,000 loan at 6.50% for 5 years yields a monthly payment of $489.15 at the end of the period, but $486.52 at the start of the period.
3. Nominal vs Effective Annual Rate (APR vs APY). A nominal 6.50% interest rate compounded monthly yields an effective annual rate (APY) of 6.697%. If your lending agreement or course sheet quotes APY, convert it to nominal first on the Interest & Dates worksheet.
4. Day count convention. Fixed-income bonds and treasury notes can use either Actual/Actual or 30/360 day counting. Across 61 days on a 5% coupon, this convention difference shifts the accrued figure between 0.8356 and 0.8472.
5. Financed bank fees and rounding rules. Lenders frequently roll origination charges, documentation stamp duties, or insurance premiums into the gross principal balance, or round individual monthly installments upward to whole currency units. Enter the exact “Amount Financed” figure from your disclosure statement to compare accurately.

Still encountering a discrepancy? Send us your inputs directly through the app's support action, and we will trace the arithmetic with you step by step.

Frequently Asked Questions

Where did my calculation go after closing the app?

Everything you calculate is automatically stored in History alongside the exact register parameters and timing modes it used. Open History from the top navigation or press ⌘⇧H on iPad and Mac. If you disabled “Save every calculation” in Settings, only items you manually named or starred are retained.

How do I view and print a complete amortization schedule?

Solve any loan in the Loans & Mortgages worksheet, then tap the Amortize button. You can switch seamlessly between monthly and annual rollups, see the crossover month where principal repayment exceeds interest, and tap Export to generate a print-ready PDF or raw CSV spreadsheet.

How do I export data to Microsoft Excel or Apple Numbers?

Choose Export → CSV. On macOS and iPadOS, you can also select any table rows directly and press ⌘C; they paste into Excel, Numbers, or Google Sheets as cleanly structured columns.

My country uses a comma for decimal points

10B Calc automatically honors your device's system region. You can also explicitly customize your preferred decimal separator (period vs. comma) and thousands grouping in Settings → Number Formatting with a live real-time preview.

Does my calculation history sync across devices?

In version 1.0, your calculation history resides securely in the local sandbox on the device where you created it. End-to-end encrypted iCloud Drive sync is currently on our roadmap.

How do I restore my purchase on a new iPhone or Mac?

There is no restoration button needed. 10B Calc is a clean one-time paid app with zero in-app purchases: simply install it from the App Store using your existing Apple Account.

System Requirements

• iPhone: iOS 17.0 or later
• iPad: iPadOS 17.0 or later
• Mac: macOS 14.0 Sonoma or later (Native Apple Silicon & Intel)
• Connectivity: Fully offline. Zero account signup or server connectivity required.

Refunds

All App Store transactions and billing are handled directly by Apple. If you need to request a refund, you can do so through Apple's portal at reportaproblem.apple.com. If you are experiencing unexpected results or difficulty using a specific formula, please write to us first at admin@finmaksoftwares.in — we are committed to helping you solve it.

Contact Details

Finmak Softwares
No. 65, Saidapet Road, Vadapalani,
Chennai 600026, Tamil Nadu, India
Email: admin@finmaksoftwares.in