BenQ CP120 manual Screen size chart, Offset

Screen size chart

Maximum	Minimum
zoom	zoom

Offset

Screen Center of lens

						Projection distance
4:3 Screen Diagonal			4:3 Aspect in mm		Distance from Screen in mm			Vertical
Feet	Inches	mm	Width	Height	Min length	Average	Max length	Offset in
					(with max.		(with min.	mm
					zoom)		zoom)
4	48	1219	975	732	1752	1903	2054	91
		1500	1200	900	2155	2341	2527	113
5	60	1524	1219	914	2190	2379	2568	114
6	72	1829	1463	1097	2628	2854	3081	137
		2000	1600	1200	2874	3122	3370	150
7	84	2134	1707	1280	3066	3330	3595	160
8	96	2438	1951	1463	3503	3806	4109	183
		2500	2000	1500	3592	3902	4212	188
9	108	2743	2195	1646	3941	4282	4622	206
		3000	2400	1800	4310	4682	5054	225
10	120	3048	2438	1829	4379	4757	5135	229
		3500	2800	2100	5029	5463	5897	263
12	144	3658	2926	2195	5256	5709	6163	274
		4000	3200	2400	5747	6243	6739	300
15	180	4572	3658	2743	6569	7136	7703	343
		5000	4000	3000	7184	7804	8424	375
18	216	5486	4389	3292	7883	8563	9244	411
		6000	4800	3600	8621	9365	10109	450
25	300	7620	6096	4572	10948	11893	12838	572

There is 3% ~ 5% tolerance among these numbers due to optical component variations.

Positioning your projector 15