Forecasting sales for fourth quarter / Based on actual

[Tripleseas]

Hello ,

i'm working on a forecast for sales of the last quarter of this year 2022. in the table below you can find :

- the actual sales for each products during these last 3 quarters ( from january to Septembre )
- the actual sales for these products during last year.
- i calculated the weight of each products in the total production of last year.

I want to forecast the sales for this fourth quarter in 2022 in order to calculate the landing for this year in each product.
As you can see and in our field of business, there a seasonality in our trend. so doong a linear regression model is not right. i was thinking of trying a sesonality index or something like that.

i'm just putting this out there for any statistician than can help us please.
i'm using Excel 2013.
thank you all.

Forecasting.xlsx
	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R
1	DATA OF THIS YEAR : Actual sales 2022 ( 9 month )	Quarter 1 2022			Quarter 2 2022			Quarter 3 2022			Total of 9 month	Quarter 4 Foercast			Total of the year
2	Actual sales	January	February	March	April	May	June	July	August	September	Sum of 9 month	October	Novembre	December
3	Product 1	859,220	824,921	952,569	895,855	734,612	897,490	855,692	965,723	727,860	7,713,942	??	??	??	??
4	Product 2	196,136	175,669	207,709	220,015	163,775	173,022	181,296	168,666	145,565	1,631,853	??	??	??	??
5	Product 3	168,784	158,254	182,058	173,480	143,930	168,110	155,966	171,230	128,804	1,450,616	??	??	??	??
6	Product 4	126,798	115,506	138,591	159,161	116,935	130,185	132,303	140,419	123,224	1,183,122	??	??	??	??
7	Product 5	95,799	88,658	104,157	114,994	85,435	88,606	83,591	78,027	61,959	801,226	??	??	??	??
8	Product 6	15,396	29,927	52,742	34,505	48,855	70,104	105,595	143,014	73,926	574,064	??	??	??	??
9	Product 7	61,964	58,543	73,687	88,296	65,714	67,094	69,399	39,794	33,905	558,396	??	??	??	??
10	Product 8	10,793	17,853	19,910	11,541	12,585	13,829	6,041	8,327	14,328	115,207	??	??	??	??
11
12
13	DATA OF LAST YEAR : actual sales
14		Quarter 1 2021			Quarter 2 2021			Quarter 3 2021			Quarter 4 2021
15	Actual sales	January	February	March	April	May	June	July	August	September	October	November	December	Sum of the year 2021	Weight Q1	Weight Q2	Weight Q3	Weight Q4
16	Product 1	925,266	870,761	1,003,751	924,835	840,109	903,884	1,010,513	863,088	920,999	900,851	930,244	961,595	11,055,896	25.32%	24.14%	25.28%	25.26%
17	Product 2	216,967	193,482	232,798	252,909	243,971	200,811	221,814	174,339	186,926	181,772	182,891	213,904	2,502,584	25.70%	27.88%	23.30%	23.12%
18	Product 3	178,503	171,211	192,697	183,817	163,074	171,410	195,951	160,136	163,944	190,145	200,383	203,306	2,174,577	24.94%	23.83%	23.91%	27.31%
19	Product 4	116,499	113,918	135,703	152,709	161,294	123,379	138,175	100,571	114,684	118,992	120,603	138,488	1,535,015	23.85%	28.49%	23.02%	24.63%
20	Product 5	94,007	90,993	107,851	122,327	125,970	98,845	108,112	80,445	90,517	89,854	92,260	105,399	1,206,580	24.27%	28.77%	23.13%	23.83%
21	Product 6	34,708	26,218	25,643	16,164	13,674	31,304	85,899	117,983	79,954	66,507	62,747	28,180	588,981	14.70%	10.38%	48.19%	26.73%
22	Product 7	35,896	37,304	46,028	57,633	63,378	45,272	54,355	40,848	44,483	48,720	51,104	62,397	587,418	20.30%	28.31%	23.78%	27.62%
23	Product 8	12,700	32,156	32,188	19,356	11,428	11,431	5,372	5,003	11,362	12,937	13,384	18,878	186,195	41.38%	22.67%	11.67%	24.28%
2022

Cell Formulas
Range	Formula
O16	O16	=(B16+C16+D16)/$N$16
P16:P23	P16	=(E16+F16+G16)/N16
Q16:Q23	Q16	=(H16+I16+J16)/N16
R16:R23	R16	=(K16+L16+M16)/N16
O17	O17	=(B17+C17+D17)/$N$17
O18	O18	=(B18+C18+D18)/$N$18
O19	O19	=(B19+C19+D19)/$N$19
O20	O20	=(B20+C20+D20)/$N$20
O21	O21	=(B21+C21+D21)/$N$21
O22	O22	=(B22+C22+D22)/$N$22
O23	O23	=(B23+C23+D23)/$N$23

 

[Tripleseas]

Hello community,
Is there any solution to this.
Appreciate your help.
Thanks