Donald Trump's tax proposals would increase the US federal debt by US$5.3 trillion over the next decade, according to analysis from a non-partisan financial group.
This compares with US$200bn if Hillary Clinton's ideas were enacted.
The Committee for a Responsible Federal Budget looked at Mr Trump's newly revised tax plan as well as other proposals.
The panel said it could not be certain of the actual size of Mr Trump's tax proposals because his campaign will not spell out how it will treat certain businesses' tax liabilities.
Instead, the committee took a "mid-range guess" between two estimates provided by the non-partisan Tax Foundation.
When the Republican presidential hopeful introduced his economic plan last week, he vowed that his tax cuts would be paid for partly by triggering record economic growth, but the committee was sceptical and presumed these steps would generate no new growth.
Several economists have projected that Mr Trump's economic agenda - especially his restrictions on immigration and trade - would slow economic growth and possibly cause a recession.
He has also proposed a sharp increase in spending on the military and veterans. He has proposed some spending cuts, but the committee calculated they would not come close to balancing the budget.
The cost of Ms Clinton's plan comes largely from her proposals for free college in some circumstances, child care aid and universal nursery care for four-year-olds.
She proposes paying for them with tax hikes on the rich and businesses.