What Are GDS/TDS Ratios Anyways?

Sarah Hainsworth • December 25, 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.


Sarah Hainsworth
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Everything You Should Know Before Buying a Home

By Sarah Hainsworth • September 10, 2025
Thinking About Buying a Home? Here’s What to Know Before You Start Whether you're buying your very first home or preparing for your next move, the process can feel overwhelming—especially with so many unknowns. But it doesn’t have to be. With the right guidance and preparation, you can approach your home purchase with clarity and confidence. This article will walk you through a high-level overview of what lenders look for and what you’ll need to consider in the early stages of buying a home. Once you’re ready to move forward with a pre-approval, we’ll dive into the details together. 1. Are You Credit-Ready? One of the first things a lender will evaluate is your credit history. Your credit profile helps determine your risk level—and whether you're likely to repay your mortgage as agreed. To be considered “established,” you’ll need: At least two active credit accounts (like credit cards, loans, or lines of credit) Each with a minimum limit of $2,500 Reporting for at least two years Just as important: your repayment history. Make all your payments on time, every time. A missed payment won’t usually impact your credit unless you’re 30 days or more past due—but even one slip can lower your score. 2. Is Your Income Reliable? Lenders are trusting you with hundreds of thousands of dollars, so they want to be confident that your income is stable enough to support regular mortgage payments. Salaried employees in permanent positions generally have the easiest time qualifying. If you’re self-employed, or your income includes commission, overtime, or bonuses, expect to provide at least two years’ worth of income documentation. The more predictable your income, the easier it is to qualify. 3. What’s Your Down Payment Plan? Every mortgage requires some amount of money upfront. In Canada, the minimum down payment is: 5% on the first $500,000 of the purchase price 10% on the portion above $500,000 20% for homes over $1 million You’ll also need to show proof of at least 1.5% of the purchase price for closing costs (think legal fees, appraisals, and taxes). The best source of a down payment is your own savings, supported by a 90-day history in your bank account. But gifted funds from immediate family and proceeds from a property sale are also acceptable. 4. How Much Can You Actually Afford? There’s a big difference between what you feel you can afford and what you can prove you can afford. Lenders base your approval on verifiable documentation—not assumptions. Your approval amount depends on a variety of factors, including: Income and employment history Existing debts Credit score Down payment amount Property taxes and heating costs for the home All of these factors are used to calculate your debt service ratios—a key indicator of whether your mortgage is affordable. Start Early, Plan Smart Even if you’re months (or more) away from buying, the best time to start planning is now. When you work with an independent mortgage professional, you get access to expert advice at no cost to you. We can: Review your credit profile Help you understand how lenders view your income Guide your down payment planning Determine how much you can qualify to borrow Build a roadmap if your finances need some fine-tuning If you're ready to start mapping out your home buying plan or want to know where you stand today, let’s talk. It would be a pleasure to help you get mortgage-ready.

Mortgage Approval 101: GDS & TDS Explained

By Sarah Hainsworth • September 3, 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.