GDS/TDS Ratios Explained

Tanya Toye • February 28, 2024

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.

Tanya Toye

Mortgage Broker

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Mortgage Approval 101: GDS & TDS Explained

By Tanya Toye • August 13, 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. 2. 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 Or Variable Rate Mortgage?

By Tanya Toye • August 6, 2025
If you're looking to buy a new property, refinance, or renew an existing mortgage, chances are, you're considering either a fixed or variable rate mortgage. Figuring out which one is the best is entirely up to you! So here's some information to help you along the way. Firstly, let's talk about the fixed-rate mortgage as this is most common and most heavily endorsed by the banks. With a fixed-rate mortgage, your interest rate is "fixed" for a certain term, anywhere from 6 months to 10 years, with the typical term being five years. If market rates fluctuate anytime after you sign on the dotted line, your mortgage rate won't change. You're a rock; your rate is set in stone. Typically a fixed-rate mortgage has a higher rate than a variable. Alternatively, a variable rate is not set in stone; instead, it fluctuates with the market. The variable rate is a component (either plus or minus) to the prime rate. So if the prime rate (set by the government and banks) is 2.45% and the current variable rate is Prime minus .45%, your effective rate would be 2%. If three months after you sign your mortgage documents, the prime rate goes up by .25%, your rate would then move to 2.25%. Typically, variable rates come with a five-year term, although some lenders allow you to go with a shorter term. At first glance, the fixed-rate mortgage seems to be the safe bet, while the variable-rate mortgage appears to be the wild card. However, this might not be the case. Here's the problem, what this doesn't account for is the fact that a fixed-rate mortgage and a variable-rate mortgage have two very different ways of calculating the penalty should you need to break your mortgage. If you decide to break your variable rate mortgage, regardless of how much you have left on your term, you will end up owing three months interest, which works out to roughly two to two and a half payments. Easy to calculate and not that bad. With a fixed-rate mortgage, you will pay the greater of either three months interest or what is called an interest rate differential (IRD) penalty. As every lender calculates their IRD penalty differently, and that calculation is based on market fluctuations, the contract rate at the time you signed your mortgage, the discount they provided you at that time, and the remaining time left on your term, there is no way to guess what that penalty will be. However, with that said, if you end up paying an IRD, it won't be pleasant. If you've ever heard horror stories of banks charging outrageous penalties to break a mortgage, this is an interest rate differential. It's not uncommon to see penalties of 10x the amount for a fixed-rate mortgage compared to a variable-rate mortgage or up to 4.5% of the outstanding mortgage balance. So here's a simple comparison. A fixed-rate mortgage has a higher initial payment than a variable-rate mortgage but remains stable throughout your term. The penalty for breaking a fixed-rate mortgage is unpredictable and can be upwards of 4.5% of the outstanding mortgage balance. A variable-rate mortgage has a lower initial payment than a fixed-rate mortgage but fluctuates with prime throughout your term. The penalty for breaking a variable-rate mortgage is predictable at 3 months interest which equals roughly two and a half payments. The goal of any mortgage should be to pay the least amount of money back to the lender. This is called lowering your overall cost of borrowing. While a fixed-rate mortgage provides you with a more stable payment, the variable rate does a better job of accommodating when "life happens." If you’ve got questions, connect anytime. It would be a pleasure to work through the options together.