I am assuming that we are talking about a bar that has a uniform cross-sectional shape along its full length. Hectare is a metric system area unit. Measurement Units Conversion Chart Math Calculate Area Math Measurement Follow along to learn how to calculate yourself or simply use the calculator above. How to calculate area into square meters . Hectares to square meters formula. To calculate a rectangular rooms area in square meters multiply its length in meters by its width in meters. To calculate the same area in square meters divide the result by 10763910417. For example a field might be measured at 5000000000 square millimeters when 5000 square meters would be a much easier size to say write and visualize. If you have an irregular shape you may need to break it up into smaller shapes with a known formula for the area. If the room is an odd shape break the shape down into individual rectangles calculate the area in square meters for each rectangle and then add the areas...