Act on the result
Reconcile each period against the facility statement before using the total in a decision.
Educational only: Business decision support, not accounting, tax or legal advice.
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Update policy: Reviewed when formulas or official dependencies change.
Scope: Market-neutral small-business planning using your own assumptions.
What this planner helps you decide
Best for
Businesses reconciling interest across changing principal, draws, repayments and contract terms.
Outputs
Average principal and interest by period, total interest cost and ending principal.
Start here
Enter the opening principal, then roll draws and repayments through two consistent periods.
Use a different tool when: Do not use this to compare periodic loan repayments and total interest across financing terms; use Business Loan Repayment Planner for that decision. Use this tool to compare total interest under rate, drawdown and repayment scenarios.
Cash & growth
Business Interest Cost: average principal and interest by period
Average principal and interest by period, total interest cost and ending principal.
Amounts use the same currency as your inputs. No currency conversion is performed.
Chronological interest periods
PDF and CSV exports stay on this device. Clean page links contain no inputs.
Add or remove periods from 1 to 60. Each opening balance is derived from the prior closing balance. Draws and repayments are assumed to occur evenly through each period, so the midpoint of opening and closing principal is the interest basis.
- Collection total interest
- 2,100.00
- Period 1 average principal
- 10,500.00
- Period 1 interest cost
- 1,050.00
- Period 2 average principal
- 10,500.00
- Period 2 interest cost
- 1,050.00
- Total interest cost
- 2,100.00
- Ending principal
- 10,000.00
Both series and the fallback table come from the chronological engine rows.
Closing principalCumulative interest
| Period | Closing principal | Cumulative interest |
|---|---|---|
| 1 | 11,000.00 | 1,050.00 |
| 2 | 10,000.00 | 2,100.00 |
| period-1 | Closing 11,000.00 | Cumulative interest 1,050.00 |
|---|---|---|
| period-2 | Closing 10,000.00 | Cumulative interest 2,100.00 |
Scenario comparison
Save an immutable baseline, then edit the collection to see the exact result change.
Calculation details
View calculation detailsView the formulas and inputs used for these results.
Period 1 average principal
Period 1 average principal
(period 1 opening principal + closing principal) ÷ 210,500Result10,500.00
Uses the editable chronological period collection. Raw precision retained.
Interest collection formulas →Inputs used by these formula steps
- Period 1 average principalOpening Principal
- 10,000
- Period 1 average principalPeriod Count
- 2
Period 1 interest cost
Period 1 interest cost
period 1 average principal × annual rate × days ÷ day-count basis1,050Result1,050.00
Uses the editable chronological period collection. Raw precision retained.
Interest collection formulas →Inputs used by these formula steps
- Period 1 interest costOpening Principal
- 10,000
- Period 1 interest costPeriod Count
- 2
Period 2 average principal
Period 2 average principal
(period 2 opening principal + closing principal) ÷ 210,500Result10,500.00
Uses the editable chronological period collection. Raw precision retained.
Interest collection formulas →Inputs used by these formula steps
- Period 2 average principalOpening Principal
- 10,000
- Period 2 average principalPeriod Count
- 2
Period 2 interest cost
Period 2 interest cost
period 2 average principal × annual rate × days ÷ day-count basis1,050Result1,050.00
Uses the editable chronological period collection. Raw precision retained.
Interest collection formulas →Inputs used by these formula steps
- Period 2 interest costOpening Principal
- 10,000
- Period 2 interest costPeriod Count
- 2
Total interest cost
Total interest cost
sum of interest cost across all chronological periods2,100Result2,100.00
Uses the editable chronological period collection. Raw precision retained.
Interest collection formulas →Inputs used by these formula steps
- Total interest costOpening Principal
- 10,000
- Total interest costPeriod Count
- 2
Ending principal
Ending principal
closing principal from the final chronological period10,000Result10,000.00
Uses the editable chronological period collection. Raw precision retained.
Interest collection formulas →Inputs used by these formula steps
- Ending principalOpening Principal
- 10,000
- Ending principalPeriod Count
- 2
Inputs used
- Period count
- 2
Open this calculator with preset values
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| Parameter | Meaning | Unit | Allowed values | Presence | Default |
|---|---|---|---|---|---|
| openingPrincipal | Principal at the start of period 1. Use one consistent currency and time basis. | currency units of principal at start of period 1 | 0 to 100000000 | Required | 10000 |
| period1AnnualInterestRate | User-entered annual contract rate for period 1. | decimal annual contract interest rate applied in period 1 (1 = 100%) | 0 to 1 | Required | 0.1 |
| period1DayCountBasis | Contractual annual day-count basis for period 1. | whole days/annual contract day-count basis for period 1 | 1 to 366 | Required | 365 |
| period1Days | Interest-accrual days in period 1. | interest-accrual days in period 1 | 0 to 3650 | Required | 365 |
| period1Draws | Additional principal drawn in period 1. Use one consistent currency and time basis. | currency units of principal drawn in period 1 | 0 to 100000000 | Required | 2000 |
| period1Repayments | Principal repaid in period 1. Use one consistent currency and time basis. | currency units of principal repaid in period 1 | 0 to 100000000 | Required | 1000 |
| period2AnnualInterestRate | User-entered annual contract rate for period 2. | decimal annual contract interest rate applied in period 2 (1 = 100%) | 0 to 1 | Required | 0.1 |
| period2DayCountBasis | Contractual annual day-count basis for period 2. | whole days/annual contract day-count basis for period 2 | 1 to 366 | Required | 365 |
| period2Days | Interest-accrual days in period 2. | interest-accrual days in period 2 | 0 to 3650 | Required | 365 |
| period2Draws | Additional principal drawn in period 2. Use one consistent currency and time basis. | currency units of principal drawn in period 2 | 0 to 100000000 | Required | 0 |
| period2Repayments | Principal repaid in period 2. Use one consistent currency and time basis. | currency units of principal repaid in period 2 | 0 to 100000000 | Required | 1000 |
Business Interest Cost: average principal and interest by period
Interest follows the entered average principal, annual rate and contractual day-count basis.
Formula summary
- Primary formula
- period 1 interest cost + period 2 interest cost
Data used here
- The estimate uses your inputs and the general business formula documented in the methodology.
Decision checks
Stress-test the decision
Test additional draws, slower repayments and a higher rate in the later period.
When this estimate can be misleading
- This model excludes lender fees, tax effects, covenant wording and lender-specific assessments.
- Results depend on complete, consistently classified inputs.
- Demand, timing, quality and strategic fit remain separate decisions.
- This is educational business decision support, not accounting, tax, legal or financial advice.
- Interest follows the entered average principal, annual rate and contractual day-count basis.
Educational estimate, not advice. See all assumptions & limitations →
Related reading
Guides to interpret the decision and its assumptions.
- Business Borrowing: Repayment and Cash Coverage
Review repayment, total interest, a declared cash-based affordability ceiling and downside debt-service coverage without treating a ratio as lender approval.
Read guide
Frequently asked questions
How do I compare total interest under rate, drawdown and repayment scenarios?
Reconcile each period against the facility statement before using the total in a decision.
Which planning assumptions should I stress-test?
Compare a plausible alternative scenario and verify the decision-critical assumption that changes the plan most.