Calculate the Volume of concrete in V1
Volume V1 = L x B x h
Volume V2 = H/3 (A 1 + A2 + √(A1 x A2))

Here A1 = Area of bottom of footing

A2 = Area of top of footing

the values of A1 & A2

A1 = L x B

A2 = L1 X B1

Click Here To See What Is A Lintel Beam? A Comprehensive Guide