could estimate
Regular verb: estimate - estimated- estimated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could estimate
you could estimate
she could estimate
we could estimate
you could estimate
they could estimate 	I could be estimating
you could be estimating
she could be estimating
we could be estimating
you could be estimating
they could be estimating	I could have estimated
you could have estimated
she could have estimated
we could have estimated
you could have estimated
they could have estimated	I could have been estimating
you could have been estimating
she could have been estimating
we could have been estimating
you could have been estimating
they could have been estimating	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't estimate
you couldn't estimate
she couldn't estimate
we couldn't estimate
you couldn't estimate
they couldn't estimate 	I couldn't be estimating
you couldn't be estimating
she couldn't be estimating
we couldn't be estimating
you couldn't be estimating
they couldn't be estimating	I couldn't have estimated
you couldn't have estimated
she couldn't have estimated
we couldn't have estimated
you couldn't have estimated
they couldn't have estimated	I couldn't have been estimating
you couldn't have been estimating
she couldn't have been estimating
we couldn't have been estimating
you couldn't have been estimating
they couldn't have been estimating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I estimate?
could you estimate?
could she estimate?
could we estimate?
could you estimate?
could they estimate? 	could I be estimating?
could you be estimating?
could she be estimating?
could we be estimating?
could you be estimating?
could they be estimating? 	could I have estimated?
could you have estimated?
could she have estimated?
could we have estimated?
could you have estimated?
could they have estimated? 	could I have been estimating?
could you have been estimating?
could she have been estimating?
could we have been estimating?
could you have been estimating?
could they have been estimating? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I estimate?
couldn't you estimate?
couldn't she estimate?
couldn't we estimate?
couldn't you estimate?
couldn't they estimate? 	couldn't I be estimating?
couldn't you be estimating?
couldn't she be estimating?
couldn't we be estimating?
couldn't you be estimating?
couldn't they be estimating? 	couldn't I have estimated?
couldn't you have estimated?
couldn't she have estimated?
couldn't we have estimated?
couldn't you have estimated?
couldn't they have estimated? 	couldn't I have been estimating?
couldn't you have been estimating?
couldn't she have been estimating?
couldn't we have been estimating?
couldn't you have been estimating?
couldn't they have been estimating?