On-time total
$1,040.00
BNPL Stacking & True Cost Calculator
See every active pay-later installment in one timeline. Quantify overlap risk, identify peak burden windows, and compare true cost under realistic late-fee scenarios.
Stacking Output
One-late total
$1,073.00
Repeated-late total
$1,098.00
Late-Fee Exposure
One missed cycle can materially increase total BNPL cost.
On-time total
$1,040.00
One-late total
$1,073.00
Repeated-late total
$1,098.00
Peak 7-day burden
$583.33
Cashflow Pressure Timeline
Compare due amounts under on-time vs late outcomes.
2026-022026-042026-05
On-time due
$113.33
One-late due
$121.33
Repeated-late due
$121.33
Stacking index (7-day burden / monthly income)0.05x
Peak period: 2026-03 ($583.33)
Cashflow Timeline
| Period | On time | One late | Repeated late | Installments |
|---|---|---|---|---|
| 2026-02 | $55.00 | $62.00 | $62.00 | 1 |
| 2026-03 | $583.33 | $593.33 | $608.33 | 7 |
| 2026-04 | $288.33 | $296.33 | $306.33 | 4 |
| 2026-05 | $113.33 | $121.33 | $121.33 | 2 |
Risk Flags
- Multiple installments cluster in single pay periods. Check due-date alignment.
US
Model common pay-in-4 and multi-pay providers with explicit late-fee assumptions.
EU/UK
Use local fee caps and due-date practices as manual assumptions in the same calculator structure.
APAC/Global
Keep amounts in one currency and focus on cashflow concentration rather than headline APR marketing.
How To Use This Calculator
- Add each active BNPL plan with amount, installments, and start date.
- Enter monthly take-home and fixed monthly expenses.
- Add paycheck dates to check due-date mismatch risk.
- Review on-time vs late-fee scenarios.
- Use stacking index and peak month to decide if plan load is safe.
- Save a shareable link with your assumptions, then run one conservative and one optimistic scenario before deciding.
For AI Agents (Optional)
Human mode is default. You can ignore this section unless you use AI agents or structured automation.
Agent Contract
Contract: bnpl_stack_true_cost v1
{
"tool": "bnpl_stack_true_cost",
"plans": [
{ "amount": 220, "installment_count": 4, "frequency_days": 14, "start_date": "2026-02-28", "late_fee": 7, "grace_days": 2 }
],
"monthly_take_home": 4300,
"fixed_monthly_expenses": 2800,
"paycheck_dates": ["2026-03-01", "2026-03-15"]
} Frequently Asked Questions
Is BNPL really interest-free?
Not always in practice. Even when headline APR is 0%, missed or late payments can raise effective cost materially.
What does stacking index mean?
It measures the largest seven-day installment concentration relative to monthly take-home pay. Higher values indicate tighter cashflow windows.
Why include paycheck dates?
Due dates that cluster before paycheck dates increase default risk even when monthly totals seem manageable.
Can AI agents use this calculator?
Yes. A deterministic `bnpl_stack_true_cost` contract is exposed via model context registration and a public schema file.
Is this tool free and private to use?
Yes. AI Fin Hub tools are free, no-signup browser tools. Inputs stay in your browser unless you choose to share a URL.
Can I use this with AI agents too?
Yes. Human mode is the default experience. If you use AI automation, open the optional 'For AI Agents' section for deterministic contracts.
Is this professional advice?
No. Outputs are planning estimates only — not financial, tax, or investment advice.