This bill discount calculator, provided by Hesapstan, helps you estimate the present cash value of a bill, note, or similar time-dated receivable from nominal value, annual rate, and time to maturity. It supports both Turkish dış iskonto, often explained as outer or bank discount, and iç iskonto, often explained as inner or true discount. The result is a mathematical commercial-finance calculation based on your inputs, not a bank quote, legal instruction, or guarantee of the actual amount a financial institution will pay.
What does a bill discount calculation show?
A bill discount calculation estimates how much a future nominal amount is worth today under a chosen annual rate and time-to-maturity assumption. The nominal value is the amount written on the bill at maturity; the present cash value is the amount after applying the selected discount method.
This calculator returns the present value, the discount amount, the method used, the rate, and the duration. It is designed for commercial-finance discounting of bills or notes, not for retail price discounts on products.
The calculation excludes commissions, taxes, bank fees, credit-risk pricing, customer-specific terms, and the actual contract offered by a bank or lender. Use it as a formula result, not as an institution's binding quote.
Inner discount and outer discount
In Turkish commercial-finance terminology, dış iskonto calculates the discount amount directly on the nominal value. This is commonly mapped to outer discount or bank discount in English explanations. Because the deduction is taken from the full nominal value, the present value can drop sharply when rate and time are large.
İç iskonto calculates the present value first and then takes the difference between nominal and present value as the discount. This is commonly mapped to inner discount or true discount. For the same nominal value, annual rate, and duration, inner discount and outer discount can produce different present values.
- Outer discount: discount is calculated on the nominal value.
- Inner discount: present value is calculated first, then the discount is the difference from nominal value.
- Both depend entirely on user-entered rate and duration.
- Neither method includes bank commissions, tax, or actual transaction terms.
How the formulas work
The calculator first converts the duration into years. Days are divided by 365, months are divided by 12, and years are used directly. The annual rate is entered as a percent and converted to a decimal rate for the calculation.
- Time factor is computed from days, months, or years.
- Outer discount uses: discount = nominal value × annual rate × time.
- Outer present value is nominal value minus the discount amount.
- Inner discount uses: present value = nominal value / (1 + annual rate × time).
- Inner discount amount is nominal value minus present value.
This calculator uses a 365-day year when the duration is entered in days. Some markets or contracts may use a 360-day convention or other day-count rules; those choices are outside this calculator's current scope.
Worked example: 100,000 nominal, 45% annual rate, 90 days
Suppose the nominal value is 100,000, the annual discount rate is 45%, and the time to maturity is 90 days. The time factor is 90 / 365 ≈ 0.2466 years.
- Outer discount: 100,000 × 0.45 × 90 / 365 ≈ 11,095.89 discount.
- Outer present value: 100,000 − 11,095.89 ≈ 88,904.11.
- Inner present value: 100,000 / (1 + 0.45 × 90 / 365) ≈ 90,012.33.
- Inner discount amount: 100,000 − 90,012.33 ≈ 9,987.67.
The example shows why choosing the method matters. Outer discount takes the deduction from the nominal amount, while inner discount discounts the maturity value back to a present value.
When this calculator is the right tool
Use this page when your question is about the present cash value of a bill, note, or dated receivable. It is not a shopping discount calculator, even though both contexts use the word discount.
- Use this calculator for inner/outer discount on a bill or promissory note.
- Use an interest calculator when you want a simple interest amount rather than a bill discount value.
- Use an average-maturity calculator when several payments with different due dates must be summarized into one maturity.
- Use purchasing-power or inflation-related tools when the issue is the value of money over time, not bill discounting.
Limitations and trust notes
The calculator explains the two methods mathematically. It does not state which method a bank, court, contract, or regulation must apply in a specific transaction.
- Outer discount can become meaningless if annual rate × time is too large and the present value becomes zero or negative.
- The calculator does not count days between two calendar dates; you enter the duration yourself.
- It does not include commissions, taxes, bank fees, BSMV-style charges, or real institution terms.
- It uses a 365-day-year convention and does not currently offer a 360-day option.
Frequently Asked Questions
Is bill discounting the same as a retail discount?
No. This calculator is for commercial-finance discounting of a bill or note. A retail discount reduces a product price; bill discounting estimates present cash value before maturity.
What is the difference between inner and outer discount?
Outer discount calculates the deduction on the nominal value. Inner discount first calculates present value and then derives the discount amount as the difference from nominal value.
Does this calculator include bank fees or taxes?
No. It excludes commissions, taxes, transaction fees, and bank-specific pricing. It is a formula calculator based only on the values you enter.
Why can outer discount show a warning?
If the annual rate multiplied by the time factor is too high, outer discount can produce a zero or negative present value. The calculator treats this as a warning state, not a normal cash value.
Can I use a 360-day year convention?
Not in this version. The days option uses a 365-day year. If your contract uses another day-count convention, adjust the duration externally or treat the result as an approximate comparison.