What Are GDS/TDS Ratios Anyways?

Carola Singer • July 5, 2023

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.


RECENT POSTS 

Selling Your Property? Let's Talk

By Carola Singer • June 25, 2025
If you’ve been thinking about selling your existing property, for whatever reason, it would be in your best interest to connect with an independent mortgage professional before calling your real estate agent or listing it yourself. And while talking with your mortgage professional might not sound like the most logical place to start, here are a few scenarios that explain why it makes the most sense. If you’re buying a new property If you’re selling your property, chances are, you’ll have to move somewhere! So, if you plan on buying a new property using the equity from the sale of your existing property, chances are you’ll need a new mortgage. Don’t assume that just because you’ve secured mortgage financing before, that you’ll qualify again. Mortgage rules are constantly changing; make sure you have a pre-approval in place before you list your property. Also, by connecting with a mortgage professional first, you can look into your existing mortgage terms. You might be able to port your mortgage instead of getting a new one, which could save you some money. If you’re not buying a new property Even if you aren’t buying a new property and want to sell your existing property, it’s still a good idea to connect with a mortgage professional first, as we can look at the cost of breaking your mortgage together. Unless you have an open mortgage, or a line of credit, there will be a penalty to break your mortgage. The goal is to work on a plan to minimize your penalty. Because of how mortgage penalties work, sometimes it’s just a matter of waiting a few months to save thousands. You'll never know unless you take a look at the details. Marital breakdown The simple truth is that marriages break down. When that happens, often, people want closure, and unfortunately, they make decisions without really thinking them through or seeing the full picture. So, instead of simply selling the family home because that feels like the only option, please know that special programs exist that allow one party to buy out the former spouse. The key here is to have a legal separation agreement is in place. If you’d like to discuss the sale of your property and your plans for the future, connect anytime. It would be a pleasure to work with you!

First-Time Homebuyer? A New GST Rebate Could Put Thousands Back in Your Pocket

By Carola Singer • June 20, 2025
If you’re a first-time homebuyer eyeing a new build or major renovation, there's encouraging news that could make homeownership significantly more affordable. The federal government has proposed a new GST rebate aimed at easing the financial burden for Canadians entering the housing market. While still awaiting parliamentary approval, the proposed legislation offers the potential for thousands in savings —and could be a game-changer for buyers trying to break into today’s high-cost housing landscape. What’s Being Proposed? Under the new legislation, eligible first-time homebuyers would receive: A full GST rebate on homes priced up to $1 million A partial GST rebate on homes between $1 million and $1.5 million This could mean up to $50,000 in tax savings on a qualifying home—a major boost for anyone working hard to save for a down payment or meet mortgage qualification requirements. Why This Matters With interest rates still elevated and home prices holding steady in many regions, affordability remains a challenge. This rebate could offer meaningful relief in several ways: Lower Upfront Costs: Removing GST from the purchase price reduces the total amount of money buyers need to save before closing. Smaller Monthly Payments: A lower purchase price leads to a smaller mortgage, which translates to more manageable monthly payments. Improved Mortgage Qualification: With a reduced purchase amount, buyers may find it easier to meet lender criteria. According to recent estimates, a homebuyer purchasing a $1 million new home could see monthly mortgage payments drop by around $240 —money that could go toward savings, home improvements, or simply everyday expenses. Helping Families Help Each Other This proposal also offers a win for parents who are supporting their children in buying a first home. Whether through gifted down payments or co-signing, a lower purchase price and more affordable monthly costs mean that family support can go further—and set first-time buyers up for long-term success. Is This the Right Time to Buy? If you’re thinking about buying a new or substantially renovated home, this proposed rebate could dramatically improve your financial position. Now is the perfect time to explore your options and make sure your mortgage strategy is aligned with potential policy changes. 📞 Let’s connect for a free mortgage review or pre-approval. Whether you’re buying your first home or helping someone else take that first step, I’m here to help you make informed, confident decisions.
More Posts