GDS/TDS Ratios Explained

Hummingbird Mortgages • June 11, 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.

Nate Atkin
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How Property Type and Condition Influence Mortgage Financing

By Hummingbird Mortgages • August 19, 2026
Why the Property Matters When You’re Qualifying for a Mortgage When qualifying for a mortgage, lenders typically look at four core areas: Income Credit Down payment or equity The property itself Most buyers focus heavily on income, credit, and savings—and for good reason. But even if those boxes are checked, the property can still determine whether a mortgage is approved. Why Lenders Care About the Property From a lender’s perspective, the property is the collateral for the mortgage. In the unlikely event of default, they need to know the home can be sold quickly and at fair market value to recover their funds. Because of this, lenders are careful about the condition, value, and marketability of any property they finance. Homes that are in poor repair, unconventional, or overpriced can raise red flags—even when the borrower is well qualified. Appraisals Are Always Part of the Process Every mortgage requires an appraisal to confirm value. Insured mortgages (through CMHC, Sagen, or Canada Guaranty) often use an automated valuation model completed online. Conventional mortgages typically require a full, on-site appraisal by a certified appraiser. This appraisal is not optional and happens after an offer is accepted—not at the pre-approval stage. Why Pre-Approvals Aren’t a Guarantee A pre-approval is a great first step, but it only assesses you, not the property. Once you’ve made an offer, the lender must approve the specific home you’re buying. Understanding this upfront helps avoid surprises and confusion later in the process. The Risk of Buying Without a Financing Condition In competitive markets, buyers sometimes remove financing conditions to strengthen their offer. However, this comes with risk. If the appraisal comes back low—or the lender is concerned about the property’s condition—you could be denied financing after the offer is firm. In that scenario, your deposit may be at risk. Buying a Home That Needs Work If you’re considering a property that isn’t in perfect condition, there are solutions. A purchase plus improvements program allows you to buy a home and include renovation costs in your mortgage. The process is structured and requires planning, but it can be an excellent way to turn a fixer-upper into a great long-term investment. Final Thoughts Mortgage approval isn’t based solely on your finances—the property matters just as much. Knowing this ahead of time helps you make smarter offers, reduce risk, and plan more effectively. If you’re buying a property that needs work or want clarity on how a lender may view a specific home, feel free to reach out. I’d be happy to walk you through your options and help you plan with confidence.

Co-Signing a Mortgage in Canada: Pros, Cons & What to Expect

By Hummingbird Mortgages • August 12, 2026
Co-Signing a Mortgage in Canada: Pros, Cons & What to Expect Thinking about co-signing a mortgage? On the surface, it might seem like a simple way to help someone you care about achieve homeownership. But before you sign on the dotted line, it’s important to understand exactly what co-signing means—for them and for you. You’re Fully Responsible When you co-sign, your name is on the mortgage—and that makes you just as responsible as the primary borrower. If payments are missed, the lender won’t only go after them; they’ll come after you too. Missed payments or default can damage your credit score and put your financial health at risk. That’s why trust is key. If you’re going to co-sign, make sure you have a clear picture of the borrower’s ability to manage payments—and consider monitoring the account to protect yourself. You’re Committed Until They Can Stand Alone Co-signing isn’t temporary by default. Even once the initial mortgage term ends, you won’t automatically be removed. The borrower has to re-qualify on their own, and only then can your name be taken off. If they don’t qualify, you stay on the mortgage for another term. Before agreeing, talk openly about expectations: How long might you be on the mortgage? What’s the plan for eventually removing you? Having these conversations upfront prevents surprises later. It Affects Your Own Borrowing Power When lenders calculate your debt service ratios, the co-signed mortgage counts as your debt—even if you never make a payment on it. This could reduce how much you’re able to borrow in the future, whether it’s for your own home, an investment property, or even refinancing. If you see another mortgage in your future, you’ll want to consider how co-signing could limit your options. The Upside: Helping Someone Get Ahead On the positive side, co-signing can be life-changing for the borrower. You could be helping a family member or friend buy their first home, start building equity, or take an important step forward financially. If handled with clear expectations and trust, it can be a meaningful way to support someone you care about. The Bottom Line Co-signing a mortgage comes with both risks and rewards. It’s not a decision to take lightly, but with careful planning, transparency, and professional advice, it can be done responsibly. If you’re considering co-signing—or want to explore safer alternatives—let’s connect. I’d be happy to walk you through what to expect and help you decide if it’s the right move for you.