COFI vs SOFR ARM 2027 Comparison Calculator

Compare 5/1 ARM payments under COFI vs SOFR index 2027 — see which adjustable-rate index produces lower payment after reset.

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COFI Index

Cost of Funds Index — weighted average of interest paid on deposits by 11th District lenders. Lags market by 3-6 months. Slower-moving than SOFR. Last published monthly by Federal Home Loan Bank of San Francisco.

SOFR Index

Secured Overnight Financing Rate — published by NY Fed. Replaced LIBOR June 2023. Most modern ARMs use 30-day average SOFR. Faster-moving but transparent.

How Margin Works

ARM rate = Index + Margin. Margin is fixed for life of loan (typically 2.25-3%). Lender picks margin at origination. The lower the margin, the more competitive the loan.

Rate Cap Limits

All conforming ARMs cap initial adjustment (typ 2-5%) AND lifetime cap (typ 5% above start). Even if index spikes, your rate cannot exceed caps. Always verify on Loan Estimate.

Source: freddiemac.com (Primary Mortgage Survey), cfpb.gov ARM Disclosure. Last updated: May 2026.