Four times as much; quadruple — indicating a quantity or rate that is four times another.
昨年と比べて売上が四倍になった。
Sales have become four times compared to last year.
この箱の体積はあの箱の四倍だ。
The volume of this box is four times that of that box.
金利が四倍になると返済額に大きな影響が出る。
If the interest rate becomes four times as high, it will greatly affect the repayment amount.