This is the special credit score lenders use when you apply for a mortgage

Your credit score is a three-digit number that reflects your credit history. It's not the complete financial picture, but lenders consider it when evaluating you for lines of credit and insurance.

But there are multiple versions of your credit score.

For the majority of lending decisions most lenders use your FICO score. Calculated by the data analytics company Fair Isaac Corporation, it's based on data from credit reports about your payment history, credit mix, length of credit history and other criteria.

Some lenders use another scoring model, VantageScore, especially credit card companies.

But if you're applying for a mortgage, the score on your application might be different from either of them.

Here's what you need to know about credit scores if you're looking to buy a home.

While the FICO^® 8 model is the most widely used scoring model for general lending decisions, banks use the following FICO scores when you apply for a mortgage:

• FICO^® Score 2 (Experian)
• FICO^® Score 5 (Equifax)
• FICO^® Score 4 (TransUnion)

All the credit reporting agencies use a slightly different version of the FICO score. That's because FICO tweaks its model to best predict creditworthiness in different industries. You're still evaluated on the same core factors — payment history, credit use, credit mix and the age of your accounts— but they're weighed a little differently.

That makes sense — paying off a mortgage is different than using a credit card responsibly.

The FICO 8 model used by credit card companies is more critical of high balances on revolving credit lines. Since revolving credit is less of a factor when it comes to mortgages, the FICO 2, 4 and 5 models have proven to be reliable when evaluating candidates for a mortgage.

According to Darrin English, a senior community development loan officer at Quontic Bank, mortgage lenders request your FICO scores from all three bureaus — Equifax, Transunion and Experian. But they only use one when making their final decision.

If all of your scores are the same, the choice is simple. But what if your scores are different?

"We'll use the median as the qualifying credit score," English said. "It's called a tri-merge."

If two of the three scores are identical, lenders use that one, he added, regardless of whether it's higher or lower than the third.

If you are applying for a mortgage with a co-signer, like a spouse, each applicant's FICO 2, 4 and 5 scores are pulled. The lender identifies the median score for each of you, and then uses the lower of the two.

Knowing your credit score is the first step in getting the best rates on your mortgage.

According to FICO, a borrower with a credit score of 760 can expect an interest rate of 6.47% on a 30-year fixed mortgage. For a borrower with a score between 620 and 639 (considered subprime), that rate would be 8.05%.

A 1.58% APR savings may seem negligible, but it could save you hundreds each month and thousands over the life of the loan.

Your credit score reflects your history of paying off debt. A higher score can save you thousands in interest payments over the life of your mortgage. If you want to improve your score:

• Make on-time payments in full, especially on revolving credit like credit cards.
• Ask to increase your credit limit on existing cards
• Keep your credit utilization rate under 30%
• Avoid opening new lines of credit
• Try to get credit for utility payments

*Experian Boost™ is a free service that updates your Experian credit report with on-time payments to your mobile carrier, power company and other utilities not usually linked to credit-reporting agencies. According to the company, users whose FICO scores improve see an average increase of 13 points.

Since the mortgage industry looks at all three credit reports, consider a paid credit monitoring service that pulls more comprehensive data than a free version would.

In addition to providing regular updates on your FICO score, Experian IdentityWork℠ Premium examines data from all three credit bureaus and informs users about score changes, new inquiries and accounts, changes to your personal information and suspicious activity.

The most accurate way to keep tabs on your mortgage-specific credit score is with the advanced version of MyFICO®, which shares versions of your FICO score calculated for credit cards, home and auto loans and more for $29.95 a month.

You'll also have access to $1 million in identity theft insurance and 24-hour expert help if your identity is compromised.

Mortgage lenders use a specific version of your credit score to determine if you're a good candidate for a home loan. Make sure to monitor the credit score that matters to mortgage lenders if you're looking to buy a home soon.

At CNBC Select, we work with experts who have specialized knowledge and authority based on relevant training and/or experience. For this story, we interviewed Darrin English, a senior community development loan officer at Quontic Bank.

At CNBC Select, our mission is to provide our readers with high-quality service journalism and comprehensive consumer advice so they can make informed decisions with their money. Every review is based on rigorous reporting by our team of expert writers and editors with extensive knowledge of credit monitoring products. While CNBC Select earns a commission from affiliate partners on many offers and links, we create all our content without input from our commercial team or any outside third parties, and we pride ourselves on our journalistic standards and ethics.

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*Results may vary. Some may not see improved scores or approval odds. Not all lenders use Experian credit files, and not all lenders use scores impacted by Experian Boost.