GDS/TDS Ratios Explained

Kambi Heywood • November 9, 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 through CMHC is required, the maximum GDS is 35% with a maximum TDS of 42%. Those ratios are stretched a little when default insurance is secured through Sagan (formerly Genworth) or Canada Guarantee to 39% GDS and 44% TDS.


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.


Kambi Heywood

Licensed Mortgage Broker

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Mortgage Approval 101: GDS & TDS Explained

By Kambi Heywood • December 18, 2025
Can You Afford That Mortgage? Let’s Talk About Debt Service Ratios One of the biggest factors lenders look at when deciding whether you qualify for a mortgage is something called your debt service ratios. It’s a financial check-up to make sure you can handle the payments—not just for your new home, but for everything else you owe as well. If you’d rather skip the math and have someone walk through this with you, that’s what I’m here for. But if you like to understand how things work behind the scenes, keep reading. We’re going to break down what these ratios are, how to calculate them, and why they matter when it comes to getting approved. What Are Debt Service Ratios? Debt service ratios measure your ability to manage your financial obligations based on your income. There are two key ratios lenders care about: Gross Debt Service (GDS) This looks at the percentage of your income that would go toward housing expenses only. Total Debt Service (TDS) This includes your housing costs plus all other debt payments—car loans, credit cards, student loans, support payments, etc. How to Calculate GDS and TDS Let’s break down the formulas. GDS Formula: (P + I + T + H + Condo Fees*) ÷ Gross Monthly Income Where: P = Principal I = Interest T = Property Taxes H = Heat Condo fees are usually calculated at 50% of the total amount TDS Formula: (GDS + Monthly Debt Payments) ÷ Gross Monthly Income These ratios tell lenders if your budget is already stretched too thin—or if you’ve got room to safely take on a mortgage. How High Is Too High? Most lenders follow maximum thresholds, especially for insured (high-ratio) mortgages. As of now, those limits are typically: GDS: Max 39% TDS: Max 44% Go above those numbers and your application could be declined, regardless of how confident you feel about your ability to manage the payments. Real-World Example Let’s say you’re earning $90,000 a year, or $7,500 a month. You find a home you love, and the monthly housing costs (mortgage payment, property tax, heat) total $1,700/month. GDS = $1,700 ÷ $7,500 = 22.7% You’re well under the 39% cap—so far, so good. Now factor in your other monthly obligations: Car loan: $300 Child support: $500 Credit card/line of credit payments: $700 Total other debt = $1,500/month Now add that to the $1,700 in housing costs: TDS = $3,200 ÷ $7,500 = 42.7% Uh oh. Even though your GDS looks great, your TDS is just over the 42% limit. That could put your mortgage approval at risk—even if you’re paying similar or higher rent now. What Can You Do? In cases like this, small adjustments can make a big difference: Consolidate or restructure your debts to lower monthly payments Reallocate part of your down payment to reduce high-interest debt Add a co-applicant to increase qualifying income Wait and build savings or credit strength before applying This is where working with an experienced mortgage professional pays off. We can look at your entire financial picture and help you make strategic moves to qualify confidently. Don’t Leave It to Chance Everyone’s situation is different, and debt service ratios aren’t something you want to guess at. The earlier you start the conversation, the more time you’ll have to improve your numbers and boost your chances of approval. If you're wondering how much home you can afford—or want help analyzing your own GDS and TDS—let’s connect. I’d be happy to walk through your numbers and help you build a solid mortgage strategy.

Fixed vs. Variable Mortgage Rates in Canada

By Kambi Heywood • December 11, 2025
Fixed vs. Variable Rate Mortgages: Which One Fits Your Life? Whether you’re buying your first home, refinancing your current mortgage, or approaching renewal, one big decision stands in your way: fixed or variable rate? It’s a question many homeowners wrestle with—and the right answer depends on your goals, lifestyle, and risk tolerance. Let’s break down the key differences so you can move forward with confidence. Fixed Rate: Stability & Predictability A fixed-rate mortgage offers one major advantage: peace of mind . Your interest rate stays the same for the entire term—usually five years—regardless of what happens in the broader economy. Pros: Your monthly payment never changes during the term. Ideal if you value budgeting certainty. Shields you from rate increases. Cons: Fixed rates are usually higher than variable rates at the outset. Penalties for breaking your mortgage early can be steep , thanks to something called the Interest Rate Differential (IRD) —a complex and often costly formula used by lenders. In fact, IRD penalties have been known to reach up to 4.5% of your mortgage balance in some cases. That’s a lot to pay if you need to move, refinance, or restructure your mortgage before the end of your term. Variable Rate: Flexibility & Potential Savings With a variable-rate mortgage , your interest rate moves with the market—specifically, it adjusts based on changes to the lender’s prime rate. For example, if your mortgage is set at Prime minus 0.50% and prime is 6.00% , your rate would be 5.50% . If prime increases or decreases, your mortgage rate will change too. Pros: Typically starts out lower than a fixed rate. Penalties are simpler and smaller —usually just three months’ interest (often 2–2.5 mortgage payments). Historically, many Canadians have paid less overall interest with a variable mortgage. Cons: Your payment could increase if rates rise. Not ideal if rate fluctuations keep you up at night. The Penalty Factor: Why It Matters More Than You Think One of the biggest surprises for homeowners is the cost of breaking a mortgage early —something nearly 6 out of 10 Canadians do before their term ends. Fixed Rate = Unpredictable, potentially high penalty (IRD) Variable Rate = Predictable, usually lower penalty (3 months’ interest) Even if you don’t plan to break your mortgage, life happens—career changes, family needs, or new opportunities could shift your path. So, Which One is Best? There’s no one-size-fits-all answer. A fixed rate might be perfect for someone who wants stable budgeting and plans to stay put for years. A variable rate might work better for someone who’s financially flexible and open to market changes—or who may need to exit their mortgage early. Ultimately, the best mortgage is the one that fits your goals and your reality —not just what the bank recommends. Let's Find the Right Fit Choosing between fixed and variable isn’t just about numbers—it’s about understanding your needs, your future plans, and how much financial flexibility you want. Let’s sit down and walk through your options together. I’ll help you make an informed, confident choice—no guesswork required.