# Second Mortgage Calculator Borrowing capacity against a combined loan-to-value ceiling, the payment, and the blended rate across both liens. --- - **Canonical URL:** https://dothecalculation.com/calculators/second-mortgage-calculator - **Category:** Real Estate & Property - **Publisher:** Do The Calculation (https://dothecalculation.com) - **Cost:** Free, no account or sign-up required - **Privacy:** Runs entirely in the browser; inputs are never sent to a server - **Methodology:** https://dothecalculation.com/methodology --- ## Second Mortgage Sizing, Payment, and Combined LTV How much a lender will advance behind your first mortgage, what it costs monthly, and where the combined loan-to-value lands once it is drawn. - Available equity against an 80–85% combined loan-to-value ceiling - Fixed payment, total interest, and cost per $1,000 borrowed - Blended rate across both liens, which is the real cost of the money ## Quick Answer — How Much Can You Borrow on a Second Mortgage? Lenders size a second mortgage against a **combined loan-to-value ceiling**, typically **80% to 85%** of the home's value across both liens together. Your request is capped by that, not the other way around. • **Available Equity** = (Home Value × Max CLTV%) − First Mortgage Balance • **Loan Amount** = the lesser of what you request and what is available • **New CLTV** = (First Mortgage + Second Mortgage) ÷ Home Value × 100 • **Monthly Payment** = the ordinary amortisation formula on the second-lien balance **Worked example:** a **$540,000** home with a **$305,000** first mortgage, against an **85%** CLTV ceiling. The ceiling is **$459,000**, so available equity is **$154,000**. A **$90,000** request fits comfortably. At **8.75%** over **15 years** the payment is **$899.50** a month, with **$71,910.68** of total interest — **$9.99 a month per $1,000 borrowed**. Combined with a **$2,150** first-mortgage payment, total housing debt service is **$3,049.50**. Combined LTV rises from **56.48%** to **73.15%**, and the **blended rate across both liens is 4.89%**, because a large low-rate first mortgage dilutes an expensive second. ## How to Use This Calculator: $90,000 Behind a $305,000 First Enter the home's current value and the balance on your first mortgage. Value matters more than you might expect: at an 85% ceiling, every **$10,000** of appraised value is **$8,500** of borrowing capacity, so an appraisal that comes in low can reduce what you can borrow far more than it reduces your equity. The [home equity calculator](/calculators/home-equity-calculator) shows the underlying position. Set the CLTV ceiling your lender uses. **Eighty to eighty-five percent** is standard on a primary residence with strong credit; investment properties, second homes, and weaker credit profiles get less, sometimes considerably less. Here, 85% of $540,000 is $459,000, leaving **$154,000** of room behind the $305,000 first. Second mortgage rates run **above** first mortgage rates, typically by one to three points, because the second lienholder is paid only after the first in a foreclosure. At **8.75%** over 15 years, $90,000 costs **$899.50** a month and **$71,910.68** in interest — roughly 80% of the amount borrowed, which is what a shorter term at a higher rate produces. The **blended rate of 4.89%** is the number worth carrying away. It answers the question that actually matters when you already hold a cheap first mortgage: what does the total debt on this house cost? Borrowing $90,000 at 8.75% behind $305,000 at 3.75% is very different from refinancing the whole $395,000 at, say, 6.5% — the second mortgage keeps the cheap money in place. That comparison belongs in the [refinance break-even calculator](/calculators/refinance-break-even-calculator), and it is the main reason second mortgages regained popularity when rates rose. ## A Second Example: When the Ceiling Binds Requests are often larger than capacity. Take a **$380,000** home with a **$240,000** first mortgage and an **80%** ceiling — common on a property that is not a primary residence or where credit is thinner. The ceiling is **$304,000**, so available equity is only **$64,000** against a **$100,000** request: a **shortfall of $36,000**. The loan is capped at $64,000, which takes combined LTV to exactly **80.00%**. At **9.5%** over **20 years** the payment is **$596.56** and total interest is **$79,175.35** — more interest than on the larger loan in the first example, because a longer term at a higher rate compounds in both directions. Note what happens to the blended rate: **6.93%**, against 4.89% in the first example. The first mortgage here is at 6.25% rather than 3.75%, so it dilutes the expensive second far less. **The case for a second mortgage over a full refinance is strongest when the first mortgage rate is well below market and weakest when it is not** — if your first mortgage is already at market rate, a cash-out refinance is usually the cheaper route to the same money. The **$76,000** of remaining equity is the other thing to watch. It is the cushion between combined debt and value, and at an 80% CLTV it is thin: a 20% fall in the home's value would leave the property worth less than the loans against it. Second mortgages are cheap relative to unsecured borrowing precisely because the house secures them, and that is the risk being priced. ## Second Mortgage, HELOC, or Cash-Out Refinance? **A home equity loan (this calculator) is a fixed-rate lump sum.** You take the whole amount at closing and repay it on a set schedule, which suits a known one-off cost: a specific renovation, a debt consolidation with a fixed balance, a defined bill. The payment never changes. **A HELOC is a variable-rate revolving line.** You draw what you need during a draw period of usually five to ten years, paying interest only on what is drawn, then repay over a further ten to twenty. That flexibility suits uncertain or staged spending, at the cost of rate risk and a payment jump when the draw period ends — the [HELOC calculator](/calculators/home-equity-line-of-credit-heloc-calculator) models that structure, and the [interest-only mortgage calculator](/calculators/interest-only-mortgage-calculator) shows the same payment-shock arithmetic in a first-lien context. **A cash-out refinance replaces the first mortgage entirely.** One loan, one payment, usually at a lower rate than a second mortgage — but you give up the rate on your existing first mortgage and pay a full set of closing costs. When your current rate is well below market, that trade is usually terrible; when it is at or above market, it is usually better than a second lien. **Two practical points.** Closing costs on a second mortgage are lower than a refinance but rarely zero, and lenders offering "no cost" seconds normally price that into the rate. And a second lien has to be **subordinated** if you later refinance the first — the second lender must agree to stay behind the new first mortgage, which they usually do but not always, and not always quickly. Taking a second mortgage makes a future refinance of the first modestly more complicated. ## Limitations This calculator assumes the home value you enter is what a lender's appraisal will support, which is the assumption most likely to be wrong. Automated valuation estimates and recent neighbour sales are not appraisals, and at an 85% ceiling every dollar of appraisal shortfall reduces borrowing capacity by 85 cents. It also assumes a single fixed-rate fully amortising second lien; HELOCs, balloon-structured seconds, and interest-only seconds all behave differently. It does not include closing costs, appraisal fees, title work, or any lender points, all of which reduce the net proceeds below the loan amount shown. Nor does it model the tax treatment of the interest, which depends on how the funds are used and on whether you itemise — rules on deductibility of home equity interest are specific and are not something a payment calculator can determine. The CLTV ceiling is entered by you and treated as fixed. Real ceilings vary with credit score, occupancy, property type, income documentation, and the lender's own appetite, and the rate typically worsens as CLTV rises rather than staying flat up to the limit. The blended rate is a balance-weighted average, which is a useful summary but not an internal rate of return across two different amortisation schedules. This is a general educational tool, not lending or tax advice — compare full loan estimates and consult a qualified professional. ## Related Calculators Start from the underlying position with the [Home Equity Calculator](/calculators/home-equity-calculator), which shows what you own before a lender's ceiling is applied. If your spending is staged or uncertain rather than a single known amount, the [HELOC Calculator](/calculators/home-equity-line-of-credit-heloc-calculator) prices the revolving alternative, and the [Interest-Only Mortgage Calculator](/calculators/interest-only-mortgage-calculator) shows the payment shock that structure creates when the draw period ends. Before choosing a second lien over replacing the first, run the [Refinance Break-Even Calculator](/calculators/refinance-break-even-calculator) — the answer turns almost entirely on how far below market your existing rate is. The [Loan-to-Value Ratio](/blog/finance/loan-to-value-ratio) guide explains the ceiling that governs all of this. ## Frequently asked questions ### How much can I borrow with a second mortgage? Take the home's value times the lender's combined loan-to-value ceiling and subtract the first mortgage balance. On a $540,000 home with a $305,000 first mortgage at an 85% ceiling, that is $459,000 − $305,000 = $154,000 of available equity. ### What is combined loan-to-value? The total of all mortgage liens divided by the home's value. Adding a $90,000 second behind a $305,000 first on a $540,000 home takes CLTV from 56.48% to 73.15%. Most lenders cap it at 80% to 85% on a primary residence, and lower on investment properties. ### Why are second mortgage rates higher? Because the second lienholder is repaid only after the first in a foreclosure, so the risk is greater. Rates typically run one to three points above first mortgage rates — 8.75% against 3.75% in the worked example. ### What is a blended rate and why does it matter? The balance-weighted average rate across both liens. Borrowing $90,000 at 8.75% behind $305,000 at 3.75% gives a blended 4.89%, which is the honest comparison against refinancing everything at a single new rate. It is why second mortgages make sense when the existing first is cheap. ### Should I take a second mortgage or a cash-out refinance? It depends almost entirely on your current first mortgage rate. Well below market, keep it and take a second — the blended rate wins. At or above market, a cash-out refinance is usually cheaper despite the closing costs, because it prices the whole balance at the new rate. ### What is the difference between a second mortgage and a HELOC? A home equity loan is a fixed-rate lump sum on a set repayment schedule, suited to a known one-off cost. A HELOC is a variable-rate revolving line you draw as needed, suited to staged or uncertain spending, with rate risk and a payment jump when the draw period ends. ### What happens if I want to refinance the first mortgage later? The second lender must agree to subordinate — to stay behind the new first mortgage rather than moving into first position. They usually do, but not always and not always quickly, so a second lien makes a future refinance of the first modestly more complicated. ### How much equity should I leave in the house? At an 80% CLTV, a $380,000 home with $304,000 of combined debt has $76,000 of cushion — enough to absorb a 20% price fall and no more. The house secures the loan, which is exactly why the rate is lower than unsecured borrowing, and exactly what is at risk. ## Related concepts - **Combined Loan-to-Value** — All mortgage liens against the home divided by its value. The ceiling that decides how much a second mortgage can advance. - **Lien Position** — The order in which lenders are repaid after a foreclosure. Second position is why second mortgage rates sit above first mortgage rates. - **Subordination** — A second lender's agreement to stay behind a newly refinanced first mortgage. Usually granted, occasionally not, and never automatic. ## Related guides - [Loan-to-Value Ratio: LTV Formula, Equity, and PMI](https://dothecalculation.com/blog/finance/loan-to-value-ratio) — Learn how to calculate loan-to-value ratio, why lenders use LTV, how equity works, and how the DTC LTV calculator interprets the result. - [How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide](https://dothecalculation.com/blog/site-guides/how-to-use-calculators) — Learn the fastest reliable workflow for using Do The Calculation calculators, reading results, checking formulas, and using save, print, share, and export actions correctly. ## Related calculators - [Down Payment Assistance Savings Calculator](https://dothecalculation.com/calculators/down-payment-assistance-savings-calculator) — Value a grant, forgivable, deferred or repayable second against mortgage insurance saved and years of saving avoided. - [Home Equity Calculator](https://dothecalculation.com/calculators/home-equity-calculator) — Calculate your current home equity, loan-to-value ratio, borrowing capacity, and projected equity after years of appreciation. - [Biweekly Mortgage Payment & Payoff Accelerator](https://dothecalculation.com/calculators/biweekly-mortgage-payoff-calculator) — Compare biweekly versus monthly mortgage payment schedules to calculate how much faster you pay off your loan and total interest saved. - [Interest-Only Mortgage Calculator](https://dothecalculation.com/calculators/interest-only-mortgage-calculator) — Both payment phases, the payment shock when the interest-only period ends, and the equity forgone. - [Jumbo Loan Calculator](https://dothecalculation.com/calculators/jumbo-loan-calculator) — Check a loan against the 2026 conforming limits, price the payment and reserves, and compare ways to stay conforming. - [Bridge Loan Calculator](https://dothecalculation.com/calculators/bridge-loan-calculator) — Interest-only cost, origination points, effective annual rate, and the surplus left after the sale. --- _This calculator assumes the home value entered is what a lender's appraisal will support — at an 85% ceiling, every dollar of shortfall reduces capacity by 85 cents. It models a single fixed-rate fully amortising second lien and excludes closing costs, appraisal and title fees, and lender points, all of which reduce net proceeds. Tax treatment of the interest depends on how funds are used and is not modelled. Real CLTV ceilings vary with credit, occupancy, property type, and documentation, and rates typically worsen as CLTV rises. This is a general educational tool, not lending or tax advice — compare full loan estimates and consult a qualified professional._ --- _Source: [Do The Calculation](https://dothecalculation.com/calculators/second-mortgage-calculator). Quote freely with attribution and a link to this page._