True Cost

Fixed vs ARM Mortgage Calculator

Compare a fixed-rate mortgage against an adjustable-rate mortgage (ARM) for your home price and loan amount. See exactly when each option wins based on how long you plan to stay.

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Loan: $360,000

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Rate never changes for the life of the loan

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Max ARM rate: 10.88%
Max ARM payment: $3,248/mo

How to Read the Numbers

The holding period slider is the most important input — it determines how long the ARM has to save you money before rate adjustments potentially reverse the advantage. The break-even point is the month when cumulative fixed payments would have been cheaper. If you move before that month, the ARM wins.

The amber uncertainty band on the cost chart shows the spread between an optimistic (rates fall slightly) and pessimistic (rates rise slightly) ARM scenario — useful for visualizing your exposure.

Key Factors in This Decision

  • How long you'll stay: The single biggest variable. If your timeline is shorter than the ARM's fixed period (e.g. 5/1 ARM, move in 4 years), the ARM is nearly risk-free.
  • Income stability: ARMs reward financial flexibility. If your income is variable or your job is uncertain, a fixed payment removes one source of stress.
  • Rate environment: Taking an ARM near a historic rate peak means adjustments are more likely to be flat or downward. Taking one near historic lows carries more upside rate risk.
  • Your risk tolerance: The fixed rate buys certainty at a premium. If budgeting tightly or you dislike payment unpredictability, that premium is often worth it.

How Future Rates Affect Your ARM

After the fixed period ends, your rate adjusts annually — capped by the per-period cap (e.g. ±2%/yr) and the lifetime cap (e.g. +5% from start). In a rising rate environment, your payment could increase by hundreds of dollars per year for several years before hitting the ceiling.

The heat map on the right shows exactly how your outcomes change across different rate trajectories and holding periods. Cells turning red indicate when staying long with a rising-rate ARM becomes more expensive than a fixed mortgage.

ARMs in a Recession

During a recession, the Federal Reserve typically cuts the federal funds rate to stimulate the economy — and ARM rates often follow. This means your ARM payment could actually decrease during an economic downturn, unlike a fixed mortgage.

However, recessions also bring layoffs and income uncertainty, which makes a predictable fixed payment more valuable for financial stability. The "optimistic" rate scenario in this calculator roughly models a mild recession environment.

What Refinancing Means

Refinancing replaces your current mortgage with a new one — usually at a different rate or term. With an ARM, many borrowers plan to refinance into a fixed-rate loan before the adjustable period begins. This strategy captures the ARM's lower initial rate, then locks in certainty later.

The catch: refinancing costs 1–3% of the loan balance in closing costs. You need to stay long enough after the refi to recover those costs — typically 2–4 years. Use the "What if you refinance?" section above to model this exact scenario with your numbers.

How long do you plan to stay?

7 years

ARM saves you

$17,255

total over 7 years · neutral rate scenario

ARM Total

$179k

Fixed Total

$196k

Difference

$17k

ARM stays cheaper than fixed for the entire 30-year term

Fixed Rate
$2,335/mo
6.75% — never changes
ARM (5/1)
$2,130/mo
Adjusts after 5 years

ARM Saves (First 5 yrs)

+$12,325

ARM Payment After Yr 5

$2,130

at 5.88%

Fixed Cheaper From

Never

neutral scenario

Total Interest Paid Over 7 Years

Fixed

$162,971

Principal: $33,165Interest: $162,971

ARM (neutral)

$140,858

Principal: $38,024Interest: $140,858

ARM saves $22,113 in interest

ARM wins at 7 years

ARM is cheaper if you move before year —. At your planned 7 years, you save $17k. Risk: rates could rise $1,119/mo at the lifetime cap.

Estimate only — not financial advice.

Payment Risk Analysis

Best $1,742← ARM range →Worst $3,248
ARM neutralFixed rate

Worst-case ARM

$3,248/mo

at 10.88% (lifetime cap)

+$1,119/mo from initial (53%)

Best-case ARM

$1,742/mo

at 3.88%

Fixed: $2,335/mo — locked

Cumulative Total Cost

Amber band = uncertainty cone (optimistic to pessimistic ARM). Purple dashed = your planned holding period.

Under What Conditions Does Each Mortgage Win?

Green = ARM cheaper · Red = Fixed cheaper · Your scenario is highlighted

Hold / Rate Δ-1%/yr-0.5%/yr0%/yr+0.5%/yr+1%/yr+1.5%/yr+2%/yr+3%/yr
2yr
ARM
$5k
ARM
$5k
ARM
$5k
ARM
$5k
ARM
$5k
ARM
$5k
ARM
$5k
ARM
$5k
3yr
ARM
$7k
ARM
$7k
ARM
$7k
ARM
$7k
ARM
$7k
ARM
$7k
ARM
$7k
ARM
$7k
5yr
ARM
$12k
ARM
$12k
ARM
$12k
ARM
$12k
ARM
$12k
ARM
$12k
ARM
$12k
ARM
$12k
7yr
ARM
$24k
ARM
$21k
ARM
$17k
ARM
$14k
ARM
$10k
ARM
$6k
ARM
$2k
ARM
$2k
10yr
ARM
$57k
ARM
$41k
ARM
$25k
ARM
$6k
Fixed
$13k
Fixed
$25k
Fixed
$30k
Fixed
$30k
15yr
ARM
$124k
ARM
$93k
ARM
$37k
Fixed
$29k
Fixed
$65k
Fixed
$77k
Fixed
$84k
Fixed
$84k
20yr
ARM
$191k
ARM
$155k
ARM
$49k
Fixed
$75k
Fixed
$116k
Fixed
$130k
Fixed
$137k
Fixed
$137k
30yr
ARM
$325k
ARM
$279k
ARM
$74k
Fixed
$167k
Fixed
$218k
Fixed
$235k
Fixed
$244k
Fixed
$244k

Remaining Loan Balance Over Time

Lower balance = more equity. Dashed lines = rate extremes (worst/best case).

Amortization Comparison — Milestone Years

YearFixed BalanceFixed PaymentARM BalanceARM PaymentARM Rate
1$356,163$2,335$355,475$2,1305.88%
3$347,670$2,335$345,589$2,1305.88%
5adjusts$337,953$2,335$334,474$2,1305.88%
7$326,835$2,335$321,976$2,1305.88%
10$307,084$2,335$300,257$2,1305.88%
15$263,864$2,335$254,389$2,1305.88%
20$203,350$2,335$192,904$2,1305.88%
25$118,625$2,335$110,483$2,1305.88%
30$0$2,335$0$2,1305.88%

Want the full picture — taxes, buy vs rent comparison, and net worth projection?

See full affordability analysis →
Fixed vs ARM — Guide & Research
🏦

Fixed vs ARM: How to Choose

The choice between a fixed and adjustable-rate mortgage comes down to one question: how long do you plan to stay?ARMs start lower — typically 0.5–1% below a 30-year fixed — and that discount is pure savings as long as the rate stays fixed. The risk only materializes once the ARM starts adjusting, usually in year 5, 7, or 10.

If you know you'll sell or refinance before the ARM adjusts, you capture the savings with none of the risk. If your timeline is uncertain, a fixed rate buys peace of mind — your payment never changes regardless of what the Fed does.

0.5–1.0%

Typical ARM discount

Below 30-yr fixed

7/1 ARM

Most common ARM

Fixed for 7 yrs

+5%

Standard lifetime cap

Above starting rate

📊

Fixed vs ARM — Side-by-Side

FeatureFixed RateARM
Initial rateHigherLower (0.5–1%)
Payment certaintyComplete — never changesChanges after fixed period
Best time horizon7+ yearsUnder 7 years
Rate riskNoneAfter initial period
Initial savingsNone$100–$400/mo typical
Max rate increaseN/A+5% lifetime cap
Ideal borrowerLong-term, stability-focusedShort-term, rate-savvy
🔬

How ARMs Work — Caps, Index & Margin

An ARM has three components that determine your payment after the fixed period ends:

📌

Index (variable)

The market benchmark your rate is tied to. Most ARMs now use SOFR (Secured Overnight Financing Rate). When SOFR rises, your rate rises. When it falls, your rate can fall.

➕

Margin (fixed)

A fixed spread added on top of the index — typically 2.5–3%. Set at origination and never changes. Your rate = index + margin (subject to caps).

🛡️

Rate Caps (your protection)

Expressed as three numbers (e.g. 2/2/5): initial adjustment cap / periodic cap / lifetime cap. A 2/2/5 on a 6% ARM means the rate can never exceed 11%, and can only move 2% in any single year.

Example: 7/1 ARM at 6.25% with 2/2/5 caps

Years 1–76.25%
Year 8 (1st adj.)Up to 8.25%
Years 9+ (annual)±2% per year
Maximum ever11.25%
🎯

Which Is Right for Your Situation?

Staying 3–5 years

ARM

You'll sell before the first adjustment. Pocket the rate savings and move on with no rate risk.

Staying 5–8 years

Either — run the numbers

Depends on the ARM discount and when rates are expected to adjust. The calculator shows your exact crossover.

Staying 10+ years

Fixed

Payment certainty wins over a long horizon. The ARM's initial savings get erased once it starts adjusting to market rates.

High-rate environment

ARM (with caution)

If rates are near cycle highs, an ARM lets you capture today's rates now and refinance into a fixed rate once rates fall.

Income uncertain / tight budget

Fixed

If a rate jump of 2%+ would cause financial strain, don't gamble on rate stability. Fixed rate = no surprises.

❓

Fixed vs ARM — Frequently Asked Questions

What is the difference between a fixed-rate and adjustable-rate mortgage?

A fixed-rate mortgage keeps the same interest rate and monthly payment for the entire loan term — 15 or 30 years. An adjustable-rate mortgage (ARM) starts with a lower fixed rate for an initial period (typically 5, 7, or 10 years), then adjusts annually based on a market index. Fixed rates offer payment certainty; ARMs offer initial savings in exchange for future rate risk.

When does an ARM make more sense than a fixed-rate mortgage?

An ARM makes sense when you plan to sell or refinance before the initial fixed period ends. If you have a 7/1 ARM and plan to move in 5 years, you'll never experience a rate adjustment — you get all the savings with none of the risk. ARMs also make sense for buyers who expect their income to grow significantly, or who are buying during a high-rate environment and anticipate rates falling before their adjustment period.

How much lower is an ARM rate compared to a fixed rate?

The ARM initial rate discount varies with market conditions. In a normal yield curve environment, a 5/1 ARM is typically 0.5–1.0% below a 30-year fixed rate, and a 7/1 ARM runs 0.25–0.75% below. In an inverted yield curve (when short-term rates are near or above long-term rates), the discount can be minimal — sometimes under 0.25%, which weakens the case for an ARM.

What are ARM rate caps and how do they protect me?

ARM rate caps limit how much your rate can increase. They're described with three numbers — e.g. "2/2/5": the first cap limits the initial adjustment (2%), the second caps each subsequent annual adjustment (2%), and the third is the lifetime cap above your starting rate (5%). So a 5/1 ARM starting at 6% with 2/2/5 caps can never exceed 11%, and can only jump 2% in any single year.

What happens when an ARM adjusts?

When an ARM adjusts, the new rate is calculated as: margin + current index value. The index is typically SOFR (Secured Overnight Financing Rate, which replaced LIBOR). The margin is set at origination — commonly 2.5–3%. So if SOFR is 4.5% and your margin is 2.75%, your new rate would be 7.25% (subject to caps). Your payment then resets based on that rate and your remaining loan balance and term.

Is a 5/1 ARM or 7/1 ARM better?

A 5/1 ARM offers a slightly lower initial rate but adjusts after 5 years. A 7/1 ARM provides rate protection for 7 years at a slightly higher initial rate. The right choice depends on your time horizon: if you're confident you'll move or refinance within 5 years, the 5/1 saves more. If your plans are less certain, the extra 2 years of protection from a 7/1 is often worth the small rate premium.

What is the break-even year between a fixed and ARM mortgage?

The ARM break-even year is when the fixed-rate mortgage's cumulative payments become lower than the ARM's cumulative payments (after the ARM has adjusted upward). In a typical scenario — ARM starting 0.75% below fixed, adjusting to parity after year 5 — the fixed rate often becomes cheaper around years 8–12. If you sell or refinance before that crossover, the ARM wins financially.

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