What is a 3/27 ARM?
A 3/27 adjustable-rate mortgage (ARM) is a 30-year mortgage structure in which the interest rate is fixed for the first three years and is adjustable for the remaining 27 years.
The name is easy to misread. In a 3/27 ARM:
- 3 = years in the initial fixed-rate period;
- 27 = years remaining in the adjustable-rate period; and
- the 27 does not mean the rate adjusts once every 27 years.
The Consumer Financial Protection Bureau's ARM handbook specifically distinguishes 2/28 and 3/27 mortgages from formats such as 3/1 or 5/1. In a 3/1 ARM, the second number describes the reset frequency after the fixed period. In a 3/27 ARM, the second number describes the number of years for which the loan remains adjustable.
How often does a 3/27 ARM adjust?
The exact adjustment schedule comes from the loan documents. Historical 3/27 products often adjusted every six months after the first three years, although not every loan used the same terms.
That makes the contract's adjustment provisions more important than the shorthand name. A borrower should identify:
- when the first adjustment occurs;
- how often subsequent adjustments occur;
- the rate index or replacement benchmark used by the contract;
- the lender's margin;
- the initial, periodic, and lifetime rate caps; and
- any payment or prepayment provisions.
CFPB guidance emphasizes that ARM borrowers should read the actual loan terms because adjustment frequency and other mechanics can vary by product.
Index, margin, and caps
After the fixed period, an ARM rate is generally determined using a benchmark index plus a lender-set margin, subject to the caps in the contract.
The index changes with market conditions; the margin is set by the lender. Rate caps limit how far the interest rate can move at the first reset, at later resets, and over the life of the loan.
Many historical 3/27 mortgages referenced LIBOR. LIBOR is no longer a current benchmark for new U.S. consumer loans, so a legacy loan that once referenced LIBOR may now operate under contractual or statutory fallback provisions. The current note, rider, and servicer disclosures control the actual replacement mechanics for a particular mortgage.
Why were 3/27 ARMs used?
3/27 ARMs became associated with the pre-2008 subprime mortgage market because they could offer a lower introductory rate for several years before entering the adjustable period.
The lower initial payment could make a loan appear more affordable at origination, but the structure shifted interest-rate risk into later years. When the fixed period ended, a borrower could face a materially higher rate and payment if the benchmark rate had risen or if the introductory rate had been substantially below the fully indexed rate.
Simple example
Suppose a 30-year 3/27 ARM has:
- a three-year initial fixed rate;
- adjustments every six months after the fixed period;
- a contractually defined index plus a fixed margin; and
- caps limiting each rate change and the maximum lifetime rate.
Months 1 through 36 use the initial fixed rate. After that, the servicer calculates each permitted reset according to the index, margin, caps, and timing rules in the loan documents. The rate is not fixed for another 27 years.
The example is structural only. It does not represent a current mortgage offer or a forecast of future rates.
3/27 versus 3/1
A 3/27 ARM and a 3/1 ARM both begin with a three-year fixed-rate period, but the shorthand communicates different things:
| Product | First number | Second number |
|---|---|---|
| 3/1 ARM | 3 years fixed | rate generally adjusts every 1 year afterward |
| 3/27 ARM | 3 years fixed | 27 years remain adjustable; reset frequency comes from the contract |
This distinction is the central point to understand when reading older mortgage documents or references to 3/27 loans.
Risks to evaluate
The main risks are the same ones CFPB highlights for ARMs generally:
- Payment shock: the payment may rise when the introductory fixed period ends.
- Benchmark risk: the adjustable rate moves with the contract's benchmark or fallback benchmark.
- Cap structure: caps can limit increases, but they do not necessarily prevent a meaningful payment change.
- Refinancing risk: a borrower should not assume they will be able to refinance before the first reset.
- Legacy-document complexity: older 3/27 mortgages may contain benchmark and servicing provisions that differ materially from modern ARM products.
Primary sources
- CFPB Consumer Handbook on Adjustable-Rate Mortgages
- CFPB: What to look for in an ARM
- CFPB: ARM index and margin
- CFPB: ARM rate caps
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