Mortgage & Amortization Calculator
PITI + PMI monthly payment with the live 30-year principal-vs-interest curve.
100% Secure. Calculations run locally — your data never leaves your browser.
$
$
20% down · No PMI
%
yr
%
$/yr
Monthly payment (PITI + PMI)
$2,505.95
P&I $2,022.62 · Tax $366.67 · Ins $116.67
Loan principal
$320,000.00
$80,000.00 down on $400,000.00
Total interest
$408,142.36
127.5% of principal
Total of payments
$728,142.36
30 × 12 P&I payments
Cumulative principal vs interest paid
Mortgage — answers & formulas
Deep-dive formulas, definitions, and worked examples — indexed for search and ready to share.
Math HistoryItaly · c. 1425
How the % Sign Was Born
Medieval Italian merchants wrote 'per cento' (per hundred) so often that scribes began abbreviating it as 'p cento', then 'pc̄o'. By the 17th century, the lazy quill stroke had evolved into the elegant symbol we know today: a slash flanked by two tiny zeros — %.
2 / 4