Inverting Volt Amplifier

Here is a schematic of the circuit we designed. Our theoretical value for gain was R2/R1 for our R2=4.7kOhm resistor and R=2.2kOhm  was 2.136

Here is the circuit we built on the breadboard

Our true values for the resistors, on the left is the true value for our R2 resistor and on the right is the true value for our R1 resistor.

Here is the table of our Vin vs Vout values. 

Vin (v)	Vout (v)
-3	4.21
-2.5	4.21
-2	4.21
-1.5	3.21
-1	2.14
-0.5	0
0	-1.064
0.5	-2.12
1	-2.12
1.5	-2.19
2	-3.43
2.5	-3.42
3	-3.42
3.5	-3.41
4	-3.41

Here is our plot of Vin vs Vout

The graph makes sense, it follows the saturation graph. However our calculated gain in pre-lab was -2.136. But when i calculated the Vout/Vin value i got -1.327. It's off by almost half. Our circuit worked, and our approach lead to values that worked for our graph. So my only guess as to why  our gain was so off  is beacuase since its not an ideal circuit, thus the values will vary from theory.