An adjustable-rate mortgage has an initial fixed period (e.g., 5 years) after which the rate adjusts based on an index plus margin.

5 years fixed, then adjusts annually. The first number is the fixed period; the second is how often it adjusts after that.

Periodic cap limits each adjustment (e.g., 2%). Lifetime cap limits total increase from the initial rate.

When does an ARM make sense?

When you plan to sell or refinance before the fixed period ends, or when initial rates are significantly lower than fixed.

The margin is added to the index (e.g., SOFR) to determine your rate after the fixed period.

What is payment shock?

The jump in payment when the rate first adjusts. Caps limit how much it can increase.

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ARM Calculator — Adjustable-Rate Mortgage Analysis

Calculate ARM payments, worst-case scenarios, and payment shock. Compare initial rate vs capped maximum.

Concept Fundamentals

$2,398

Initial Payment

$3,648

Worst Case

11.0%

Max Rate

$838,338

Interest (Worst)

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5/1 ARM = 5 yr fixed, then annual Caps protect from runaway rates Compare break-even vs fixed Plan for payment shock

Key figures

$2,398

Initial Payment

Key figure

$3,648

Worst Case

Key figure

11.0%

Max Rate

Key figure

$838,338

Interest (Worst)

Key figure

Ready to run the numbers?

Why: ARMs offer lower initial rates but carry rate risk. Caps limit how much your payment can increase.

How: Initial payment uses fixed rate. After fixed period, rate = index + margin, subject to periodic and lifetime caps.

5/1 ARM = 5 yr fixed, then annualCaps protect from runaway rates

Sources:Freddie MacCFPB

Run the calculator when you are ready.

Calculate ARM

ARM Calculator

Adjustable-rate mortgage • Payment scenarios • Rate caps

ARM Types

ARM Details

Loan AmountPrincipal

Initial RateStart rate

Fixed Period5/1, 7/1, etc.

years

Periodic CapPer adjustment

Lifetime CapMax increase

MarginAbove index

arm_calc.sh

CALCULATED

$ analyze --type=arm

Initial Payment

$2,398

After First Adjust

$2,933

Worst Case

$3,648

Max Increase

+$1,250

ARM Calculator

Initial Payment

$2,398

numbervibe.com

Payment Scenarios

Rate Structure

Payment Over Time

Worst Case Increase

Calculation Breakdown

ARM Structure

Loan Amount$400,000

Initial Rate6%

Fixed Period5 years

Periodic Cap2%

Lifetime Cap5%

Rate Scenarios

Initial Rate6%

After First Adjustment8%

Maximum Rate (Lifetime)11%

Payment Scenarios

Initial Payment$2,398

After First Adjust$2,873

Worst Case$3,648

Max Payment Increase+$1,250

Balance at Adjustment

Balance After Fixed Period$372,217

Get AI-Powered Analysis

Get personalized ARM analysis.

1. Key Takeaways

• Always plan for worst-case payment
• Caps protect you from extreme rate swings
• Best for short-term ownership
• Have an exit strategy before adjustment
• Monitor rates and refinance options

2. Understanding ARM Structure

Cap Types

• Initial cap: First adjustment limit
• Periodic cap: Each adjustment limit
• Lifetime cap: Total max increase

Common ARMs

• 5/1 ARM: Fixed 5 years, annual adjust
• 7/1 ARM: Fixed 7 years, annual adjust
• 10/1 ARM: Fixed 10 years, annual adjust

3. How It Works

Rate = Index + Margin. Adjusts at fixed period end. Capped by periodic and lifetime caps.

4. Expert Tips

Plan exit

Refinance or sell before adjustment

Budget worst-case

Can you afford max payment?

Compare caps

Lower caps = more protection

Short-term

Best if moving in 5–7 years

5. ARM Types Reference

Type	Fixed Period	Adjustment
5/1 ARM	5 years	Annual
7/1 ARM	7 years	Annual
10/1 ARM	10 years	Annual

6. FAQ

What is ARM? Adjustable-rate mortgage; rate changes after fixed period.

What is periodic cap? Max rate increase per adjustment (e.g., 2%).

What is lifetime cap? Max total rate increase over loan life.

When to choose ARM? Short-term ownership, expect to move or refinance.

7. Quick Stats

5–10

yr typical fixed

typical periodic cap

typical lifetime cap

SOFR

common index

8. Sources

Freddie Mac, Fannie Mae ARM guidelines; CFPB mortgage resources.

9. Disclaimer

This calculator provides estimates. Actual ARM terms, caps, and rates vary by lender.

For educational and informational purposes only. Verify with a qualified professional.

💡 Money Facts

5/1

5 yr fixed

— Common

Typical periodic cap

— Per adjust

Typical lifetime cap

— Max increase

Margin

Index + margin

— Rate formula

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ARM Calculator — Adjustable-Rate Mortgage Analysis

ARM Calculator

ARM Types

ARM Details

Payment Scenarios

Rate Structure

Payment Over Time

Worst Case Increase

Calculation Breakdown

ARM Structure

Rate Scenarios

Payment Scenarios

Balance at Adjustment

Get AI-Powered Analysis

1. Key Takeaways

2. Understanding ARM Structure

Cap Types

Common ARMs

3. How It Works

4. Expert Tips

5. ARM Types Reference

6. FAQ

7. Quick Stats

8. Sources

9. Disclaimer

💡 Money Facts

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We Value Your Privacy

ARM Calculator — Adjustable-Rate Mortgage Analysis

ARM Calculator

ARM Types

ARM Details

Payment Scenarios

Rate Structure

Payment Over Time

Worst Case Increase

Calculation Breakdown

ARM Structure

Rate Scenarios

Payment Scenarios

Balance at Adjustment

Get AI-Powered Analysis

1. Key Takeaways

2. Understanding ARM Structure

Cap Types

Common ARMs

3. How It Works

4. Expert Tips

5. ARM Types Reference

6. FAQ

7. Quick Stats

8. Sources

9. Disclaimer

💡 Money Facts

Related Finance Calculators

Related Calculators

Biweekly Payment Calculator

Closing Cost Impact Calculator

Interest Only Mortgage Calculator

Loan Comparison Calculator

Mortgage Payment Calculator

Mortgage Refinance Calculator

We Value Your Privacy