GDS/TDS Ratios Explained

Tara Gentles • April 22, 2025

One of the major qualifiers lenders look at when considering your application for mortgage financing is your debt service ratios.


Now, before we get started, if you prefer to have someone walk through these calculations with you, assess your financial situation, and let you know exactly where you stand, let’s connect. There is no use in dusting off the calculator and running the numbers yourself when we can do it for you!


However, if you’re someone who likes to know the nitty-gritty of how things work instead of simply accepting that's just the way it is, this article is for you. But be warned, there are a lot of mortgage words and some math ahead; with that out of the way, let’s get started!

 

“Debt servicing” is the measure of your ability to meet all of your financial obligations. There are two ratios that lenders examine to determine whether you can debt service a mortgage.


The first is called the “gross debt service” ratio, or GDS, which is the percentage of your monthly household income that covers your housing costs. The second is called the “total debt service” ratio, or TDS, which is the percentage of your monthly household income covering your housing costs and all your other debts.


GDS is your income compared to the cost of financing the mortgage, including your proposed mortgage payments (principal and interest), property taxes, and heat (PITH), plus a percentage of your condo fees (if applicable).


Here’s how to calculate your GDS.


Principal + Interest + Taxes + Heat / Gross Annual Income


Your TDS is your income compared to your GDS plus the payments made to service any existing debts. Debts include car loans, line of credit, credit card payments, support payments, student loans, and anywhere else you’re contractually obligated to make payments.


Here’s how to calculate your TDS.


Principal + Interest + Taxes + Heat + Other Debts / Gross Annual Income


With the calculations for those ratios in place, the next step is to understand that each lender has guidelines that outline a maximum GDS/TDS. Exceeding these guidelines will result in your mortgage application being declined, so the lower your GDS/TDS, the better.


If you don’t have any outstanding debts, your GDS and TDS will be the same number. This is a good thing!


The maximum ratios vary for conventional mortgage financing based on the lender and mortgage product being offered. However, if your mortgage is high ratio and mortgage default insurance is required, the maximum GDS is 39% with a maximum TDS of 44%.


So how does this play out in real life? Well, let’s say you’re currently looking to purchase a property with a payment of $1700/mth (PITH), and your total annual household income is $90,000 ($7500/mth). The calculations would be $1700 divided by $7500, which equals 0.227, giving you a gross debt service ratio of 22.7%.


A point of clarity here. When calculating the principal and interest portion of the payment, the Government of Canada has instituted a stress test. It requires you to qualify using the government's qualifying rate (which is higher), not the actual contract rate. This is true for both fixed and variable rate mortgages.


Now let’s continue with the scenario. Let’s say that in addition to the payments required to service the property, you have a car payment of $300/mth, child support payments of $500/mth, and between your credit cards and line of credit, you’re responsible for another $700/mth. In total, you pay $1500/mth. So when you add in the $1700/mth PITH, you arrive at a total of $3200/mth for all of your financial obligations. $3200 divided by $7500 equals 0.427, giving you a total debt service ratio of 42.7%.


Here’s where it gets interesting. Based on your GDS alone, you can easily afford the property. But when you factor in all your other expenses, the TDS exceeds the allowable limit of 42% (for an insured mortgage anyway). So why does this matter? Well, as it stands, you wouldn’t qualify for the mortgage, even though you are likely paying more than $1700/mth in rent.


So then, to qualify, it might be as simple as shuffling some of your debt to lower payments. Or maybe you have 10% of the purchase price saved for a downpayment, changing the mortgage structure to 5% down and using the additional 5% to pay out a portion of your debt might be the difference you need to bring it all together.


Here’s the thing, as your actual financial situation is most likely different than the one above, working with an independent mortgage professional is the best way to give yourself options. Don’t do this alone. Your best plan is to seek and rely on the advice provided by an experienced independent mortgage professional. While you might secure a handful of mortgages over your lifetime, we do this every day with people just like you.


It’s never too early to start the conversation about mortgage qualification. Going over your application and assessing your debt service ratios in detail beforehand gives you the time needed to make the financial moves necessary to put yourself in the best financial position.


So if you find yourself questioning what you can afford or if you want to discuss your GDS/TDS ratios to understand the mortgage process a little better, please get in touch. It would be a pleasure to work with you, we can get a preapproval started right away.


Tara Gentles

CANADIAN MORTGAGE EXPERT
RECENT POSTS 

Everything You Need to Know About Second Mortgages

By Tara Gentles • December 16, 2025
What Is a Second Mortgage, Really? (It’s Not What Most People Think) If you’ve heard the term “second mortgage” and assumed it refers to the next mortgage you take out after your first one ends, you’re not alone. It’s a common misconception—but the reality is a bit different. A second mortgage isn’t about the order of mortgages over time. It’s actually about the number of loans secured against a single property —at the same time. So, What Exactly Is a Second Mortgage? When you first buy a home, your mortgage is registered on the property in first position . This simply means your lender has the primary legal claim to your property if you ever sell it or default. A second mortgage is another loan that’s added on top of your existing mortgage. It’s registered in second position , meaning the lender only gets paid out after the first mortgage is settled. If you sell your home, any proceeds go toward paying off the first mortgage first, then the second one, and any remaining equity is yours. It’s important to note: You still keep your original mortgage and keep making payments on it —the second mortgage is an entirely separate agreement layered on top. Why Would Anyone Take Out a Second Mortgage? There are a few good reasons homeowners choose this route: You want to tap into your home equity without refinancing your existing mortgage. Your current mortgage has great terms (like a low interest rate), and breaking it would trigger hefty penalties. You need access to funds quickly , and a second mortgage is faster and more flexible than refinancing. One common use? Debt consolidation . If you’re juggling high-interest credit card or personal loan debt, a second mortgage can help reduce your overall interest costs and improve monthly cash flow. Is a Second Mortgage Right for You? A second mortgage can be a smart solution in the right situation—but it’s not always the best move. It depends on your current mortgage terms, your equity, and your financial goals. If you’re curious about how a second mortgage could work for your situation—or if you’re considering your options to improve cash flow or access equity—let’s talk. I’d be happy to walk you through it and help you explore the right path forward. Reach out anytime—we’ll figure it out together.

Home Reno Dreams? Let’s Talk Mortgage Financing

By Tara Gentles • December 9, 2025
How to Use Your Mortgage to Finance Home Renovations Home renovations can be exciting—but they can also be expensive. Whether you're upgrading your kitchen, finishing the basement, or tackling a much-needed repair, the cost of materials and labour adds up quickly. If you don’t have all the cash on hand, don’t worry. There are smart ways to use mortgage financing to fund your renovation plans without derailing your financial stability. Here are three mortgage-related strategies that can help: 1. Refinancing Your Mortgage If you're already a homeowner, one of the most straightforward ways to access funds for renovations is through a mortgage refinance. This involves breaking your current mortgage and replacing it with a new one that includes the amount you need for your renovations. Key benefits: You can access up to 80% of your home’s appraised value , assuming you qualify. It may be possible to lower your interest rate or reduce your monthly payments. Timing tip: If your mortgage is up for renewal soon, refinancing at that time can help you avoid prepayment penalties. Even mid-term refinancing could make financial sense, depending on your existing rate and your renovation goals. 2. Home Equity Line of Credit (HELOC) If you have significant equity in your home, a Home Equity Line of Credit (HELOC) can offer flexible funding for renovations. A HELOC is a revolving credit line secured against your home, typically at a lower interest rate than unsecured borrowing. Why consider a HELOC? You only pay interest on the amount you use. You can access funds as needed, which is ideal for staged or ongoing renovations. You maintain the terms of your existing mortgage if you don’t want to refinance. Unlike a traditional loan, a HELOC allows you to borrow, repay, and borrow again—similar to how a credit card works, but with much lower rates. 3. Purchase Plus Improvements Mortgage If you're in the market for a new home and find a property that needs some work, a "Purchase Plus Improvements" mortgage could be a great option. This allows you to include renovation costs in your initial mortgage. How it works: The renovation funds are advanced based on a quote and are held in trust until the work is complete. The renovations must add value to the property and meet lender requirements. This type of mortgage lets you start with a home that might be more affordable upfront and customize it to your taste—all while building equity from day one. Final Thoughts Your home is likely your biggest investment, and upgrading it wisely can enhance both your comfort and its value. Mortgage financing can be a powerful tool to fund renovations without tapping into high-interest debt. The right solution depends on your unique financial situation, goals, and timing. Let’s chat about your options, run the numbers, and create a plan that works for you. 📞 Ready to renovate? Connect anytime to get started!