You can easily calculate Total Weight of RebarWeight. Here you have to input
1. Your desire unit (meter or foot)
2. Length of rebar
3. Area or width of Rebar
4. Spacing of rebar in that area or width.

Remember spacing is applicable in one direction in area. Say ifspacing is "s", length is "L" and area is "A" then Total length isL X (A*1000/s+1). From this total length this apps will calculatetotal weight in KG.