Schedule Variance indicates how much ahead or behind schedule the project is.
Schedule Variance can be calculated as using the following formula:
Schedule Variance (SV) = Earned Value (EV)  Planned Value (PV)

OR
Schedule Variance (SV) = BCWP  BCWS

The formula mentioned above gives the variance in terms of cost which will indicate how much cost of the work is yet to be completed as per schedule or how much cost of work has been completed over and above the scheduled cost.
Positive Schedule Variance Indicates we are ahead of schedule.
Negative Schedule Variance Indicates we are behind of schedule.
Schedule Variance %
Schedule Variance % indicates how much ahead or behind schedule the project is in terms of percentage.
Schedule Variance % can be calculated using the following formula:
SV % = Schedule Variance (SV) / Planned Value (PV)

OR
The formula mentioned above gives the variance in terms of percentage which will indicate how much percentage of work is yet to be completed as per schedule or how much percentage of work has been completed over and above the scheduled cost.
Positive Variance % indicates % ahead of schedule.
Negative Variance % indicates % behind of schedule.
Schedule Performance Indicator (SPI)
Schedule Performance Indicator is an index showing the efficiency of the time utilized on the project. Schedule Performance Indicator can be calculated using the following formula:
SPI = Earned Value (EV) / Planned Value (PV)

OR
The formula mentioned above gives the efficiency of the project team in utilizing the time allocated for the project.
SPI value above 1 indicates project team is very efficient in utilizing the time allocated to the project.
SPI value below 1 indicates project team is less efficient in utilizing the time allocated to the project.
To Complete Schedule Performance Indicator (TSPI)
To Complete Schedule Performance Indicator is an index showing the efficiency at which the remaining time on the project should be utilized. This can be calculated using the following formula:
TSPI = ( Total Budget  EV ) / ( Total Budget  PV )

OR
TSPI = ( Total Budget  BCWP ) / ( Total Budget  BCWS )

The formula mentioned above gives the efficiency at which the project team should utilize the remaining time allocated for the project.
TSPI value below 1 indicates project team can be lenient in utilizing the remaining time allocated to the project.
TSPI value above 1 indicates project team needs to work harder in utilizing the remaining time allocated to the project.
