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Saved Mortgage Calculator

Comprehensive mortgage and amortization worksheet with public S3-backed scenario save and retrieval.

Saved Scenarios
Do not save sensitive information. These JSON files are stored in a public S3 bucket and can be read by anyone on the internet.
Use letters, numbers, dots, dashes, and underscores.
Property & Loan Basics
$
%
Down Payment Settings
$ %
Mortgage Points Calculator Disabled
%
%
Closing Costs & Escrow Fees
%
$
$
$
$
$
Extra Payments Strategy
$
Overall Loan Summary
Loan Amount $0.00
Total Points Cost $0.00
Total Cash to Close $0.00
Scheduled Number of Payments 0
Actual Number of Payments 0
Total Early Payments $0.00
Total Interest Paid $0.00
Monthly & Annual Cost Breakdown
Base Interest Rate 0.00%
Effective Interest Rate (with Points) 0.00%
Scheduled Payment (P+I) $0.00
Monthly Savings from Points (Monthly Diff) $0.00
Points Payoff Timeline (Breakeven) 0.00 months
Taxes, Ins. HOA and PMI Monthly $0.00
Total Monthly Outlay $0.00
Net Monthly Cost $0.00
Annual Costs $0.00
Amortization Schedule
💡 You can type a Manual Custom Extra Payment directly into any row row below to simulate standalone lump-sum or variable paydowns.
Pmt # Date Beginning Bal Scheduled Pmt Manual Row Extra ($) Total Extra Pmt Principal Interest Ending Bal
View Calculation Details (Standard Mathematical Notation)
This technical guide outlines the mathematical architecture powering the calculator. Formulas are rendered in professional financial notation formats.
1. Down Payment & Financed Principal Amount
D = Vsale × (
Ppct 100
) [Percentage Mode]
D = Vfixed [Fixed Dollar Mode]
P = Vsale − D
Where Vsale represents the home purchase price, D is total equity down payment, and P is the net financed principal loan balance.
2. Discount Points Upfront Cost & Interest Rate Impact
Cpoints = P × Npaid × (
Cper_point 100
)
Reffective = Rbase − ( Npaid × ΔRper_point )
Where Npaid is the quantity of interest rate reduction points bought, and Cpoints is the additional cash requirement at closing.
3. Scheduled Monthly Amortization Formula (M) & Break-Even Analysis
r =
R / 100 k
, n = t × k
M = P × [
r(1 + r)n (1 + r)n − 1
]
ΔM = Mbaseline − Meffective
Tbreakeven =
Cpoints ΔM
Where k represents payments per year (12), t is total term years, M is the periodic installment, and Tbreakeven is the time required to recoup upfront costs in months.
4. Non-Principal Fixed Escrow Charges
Mescrow = (
Atax + Ains + Apmi + Ahoa k
)
Aggregates recurring monthly fees where A values represent annual tax appraisals, homeowner insurance policies, private mortgage insurance, and HOA dues.
5. Progressive Amortization Ledger Recurrence Relation (Period t)
It = Bt−1 × r
Pt = min(M − It , Bt−1)
Et = min(Mextra + Mrow_custom , Bt−1 − Pt)
Bt = Bt−1 − Pt − Et
Where Bt−1 is the previous row's ending principal balance, It is monthly accrued interest, Pt is scheduled equity paydown, and Bt is the resulting ending balance.