AC Waveform Calculations (Inverter Design)

I’m giving a square wave input to an inverter transformer using push pull method.

Frequency is 50Hz.
Transformer is 8.5V - 0 - 8.5V / 230V.
Battery voltage is 12V

What I want to know is

If I give 10mS ON time to each transistor, then what will be the output voltage?
If I give 5mS ON time to each transistor, then what will be the output voltage?

I need the relationship between time & output voltage.

It depends on what you mean by output voltage?

If you're talking about a modified sine inverter then the peak voltage will be the same, assuming the bandwidth of the transformer is flat up to a reasonably high frequency.

If you're talking about RMS then it will depend on the duty cycle.

[latex]V_{RMS} = \sqrt{duty}[/latex]