Mortgage Calculators

Fixed Rate Mortgage vs. LIBOR ARM

Compare a fixed-rate mortgage with an index-based ARM (historically tied to LIBOR, now SOFR). The ARM rate equals an index plus a margin.

Inputs

Loan amount

Loan term (years)

Fixed rate

ARM initial rate

Index rate (e.g. SOFR)

Margin

ARM intro period (years)

Estimates only. Change any value to recalculate instantly.

Fully-indexed ARM rate 7.25% index 4.50% + margin 2.75%

ARM initial payment $1,816.92

Fixed payment $2,075.51

ARM at fully-indexed rate $2,182.96

ARM lifetime interest $430,595 vs $427,185 fixed

Payment scenarios

ARM initial $1.8k
Fixed $2.1k
ARM fully-indexed $2.2k

Loan balance ARMFixed

An index-based ARM resets to the index plus a fixed margin — here 7.25% after the 5-year intro. The intro rate saves $258.59/mo, but over the full term the ARM's interest runs $3,410 higher than the fixed loan if the index holds.

Balance & cumulative interest by year (ARM resets to 7.25% at year 5)View table

Year	ARM balance	Fixed balance	ARM interest	Fixed interest
1	$315,689	$316,590	$17,492	$21,496
2	$311,135	$312,942	$34,742	$42,754
3	$306,325	$309,040	$51,734	$63,758
4	$301,243	$304,866	$68,455	$84,491
5	$295,874	$300,402	$84,889	$104,933
6	$291,519	$295,627	$106,197	$125,064
7	$286,837	$290,520	$127,179	$144,863
8	$281,805	$285,057	$147,810	$164,306
9	$276,395	$279,213	$168,063	$183,369
10	$270,580	$272,963	$187,911	$202,025
11	$264,329	$266,278	$207,323	$220,246
12	$257,609	$259,127	$226,266	$238,001
13	$250,385	$251,478	$244,706	$255,258
14	$242,621	$243,296	$262,605	$271,983
15	$234,274	$234,545	$279,921	$288,138
16	$225,301	$225,185	$296,611	$303,684
17	$215,656	$215,173	$312,629	$318,578
18	$205,288	$204,463	$327,924	$332,774
19	$194,142	$193,008	$342,442	$346,226
20	$182,162	$180,756	$356,125	$358,879
21	$169,283	$167,650	$368,909	$370,680
22	$155,439	$153,632	$380,728	$381,568
23	$140,557	$138,638	$391,509	$391,480
24	$124,559	$122,600	$401,175	$400,348
25	$107,363	$105,445	$409,642	$408,099
26	$88,877	$87,095	$416,819	$414,655
27	$69,006	$67,468	$422,611	$419,935
28	$47,645	$46,474	$426,913	$423,847
29	$24,683	$24,019	$429,615	$426,298
30	$0	$0	$430,595	$427,185

How this calculator works

This calculator runs entirely in your browser — nothing you enter is sent anywhere, and there is no sign-up. Change any input and the result, breakdown, and schedule update instantly.

Rate and cost fields are pre-filled with current benchmarks (Federal Reserve / Freddie Mac via FRED (St. Louis Fed)), so your first result is already realistic — replace them with your own quote to see your numbers. To weigh one option against another, use the loan comparison calculator.

30-year fixed mortgage rate, 2019–2026

Source: Freddie Mac PMMS via FRED. Annual averages; latest weekly reading shown.

Common questions

Is this calculator free, and do I need to sign up?

Yes and no — it is completely free and asks for no account or personal details. Every calculation happens in your browser, so nothing you type is stored or sent to us.

How accurate are the results?

The math is exact for the inputs you give it, but the defaults are national benchmarks — your real rate, fees, taxes, and insurance will differ. Treat the result as a close estimate to refine with a real quote.