The recent surge in mortgage rates to 7.3% changes the math for home buyers, and not in a pretty way. It is especially vexing for homeowners with lower mortgage rates who are looking to move.

Based on Barron's analysis, the median home price would need to drop 32%, to $291,181, at current mortgage rates for the national median monthly mortgage payment to remain constant. The median home sold for $429,100 in August, according to the National Association of Realtors.

Today's mortgage holder pays a median rate of 3.88% and has a median monthly mortgage payment of $1,597, according to ICE Mortgage Technology.

Assuming 20% down and a current 7.3% mortgage rate, a buyer would pay $2,353 monthly to finance the median home. That is 47% more than the current median monthly payment. Our calculations assume a 20% down payment and a 30-year mortgage.

Mortgage rates have more than doubled since 2021, which gives current homeowners little incentive to move. That has contributed to a chronic shortage of for-sale inventory in many parts of the country. The lower rates that borrowers secured in 2020 and 2021 were "great while they lasted," writes Rick Palacios, Jr., director of research at John Burns Research & Consulting. But they are "now ironically becoming a generational scourge."

"Ultralow Covid mortgages just keep getting more and more valuable," Palacios writes.

There is little reason to expect mortgage rates will fall sharply, given the recent rise in bond yields and persistent inflation that has exceeded the Federal Reserve's 2% annual target for more than five years. Nor are home prices likely to correct dramatically, at least in the near term. "I don't expect home prices to fall that much," says Nadia Evangelou, director of research at the National Association of Realtors. "More likely, affordability will improve through some combination of lower mortgage rates, higher incomes, and slower home price growth."

Current mortgage holders have accumulated a record $17.9 trillion in home equity, or an average $310,000 per homeowner, according to the property data and analytics company Cotality. While that might seem like a lot of buying power for homeowners looking to upgrade, it also makes the market much more competitive. "Having record equity doesn't necessarily help that much, because everyone else has record equity, too," says Thom Malone, principal economist at Cotality.

Most drivers of existing home sales have little do with housing economics, Malone notes. "People get divorced, people have job changes that force them to move, people's families grow, people retire," he says.

Whatever the reason, for many homeowners, moving is about to become considerably more expensive.