Around 373,000 property transactions worth a total £82bn are on hold due to the coronavirus lockdown, Zoopla has estimated.
The website said the majority of the deals were agreed between November and February and were set to have completed between April and June.
It also said that the number of sales currently being agreed was running at a tenth of levels recorded in early in March.
That means volumes have tailed off to what would normally be expected at around Christmas time.
During the coronavirus lockdown, the government has urged home movers to do all they can to come to an agreement on alternative moving dates.
People can continue to move in limited circumstances, such as where the property is vacant.
Richard Donnell, director of research and insights at Zoopla, said: “Parts of the market are at a virtual standstill as a result of the physical restrictions that have stopped new supply coming to the market and the viewing of homes for sale.
“However, the online browsing of homes for sale and buyers expressing interest in property have been rising off a low base over the last two to three weeks.
“Sales continue to be agreed in low volumes by purchasers who viewed homes ahead of the lockdown, but there is a large pipeline of agreed sales held up by the temporary suspension of the sales market worth £82bn.”
Earlier this month, the Royal Institution of Chartered Surveyors (RICS) reported that the housing market had come to “near standstill” during the lockdown.
It said sales expectations were at their lowest level since it began polling its members on the measure in 1998.