Running, or linear meter, is term often used in fabric manufacturing. For roll of fabric price is given for running meter and the width of roll is known. Now, the task is to calculate price of fabric slice of certain length and width, given the price of running meter and width of roll.
Actually, the formula is simple - find the price of square centimeter, then multiply it by slice square, that is
Update: After reading the comments I've decided to add price of square meter to the output.
Below is the calculator