Paint Calculation

Volume solids (%)

Volume solids is the volume of paint after it has dried. Paint contains solvents, resin, pigments and additives. After application of paint, the solid portion will be left on the substrates and solvents will evaporate. It is calculated as follows:

Paint is diluted with a thinner to apply it more easily in certain conditions. Addition of thinner will reduce wet film thickness compared to the original paint. To calculate corrected wet film thickness after addition of thinner, the below formula is used.

Relation between theoretical spreading rate and practical spreading rate

Theoretical spreading rate is based on the volume solids of paints and offers an accurate starting point. The practical spreading rate is estimated based on the following rule of thumb:

Application	% reduction with respect to theoretical spreading rate
Brush or roller	10 – 15
Airless spray	10 – 15
Conventional spray	40 – 50

Estimation of paint required

**Wet film thickness (µ) required to achieve desired DFT* with different volume solids (%)**

Volume solids (%)	*Specified DFT (µ)**
Volume solids (%)	20	25	30	35	40	50	60	75	90	100	125	200	250	300	350	500	1000
10	200	250	300	350	400	–	–	–	–	–	–	–	–	–	–	–	–
15	133	166	200	233	266	333	–	–	–	–	–	–	–	–	–	–	–
20	100	125	150	175	200	250	300	–	–	–	–	–	–	–	–	–	–
25	80	100	120	140	160	200	240	300	–	–	–	–	–	–	–	–	–
30	66	83	100	117	133	166	200	250	300	–	–	–	–	–	–	–	–
35	57	71	85	100	114	142	171	214	257	285	357	–	–	–	–	–	–
40	50	62	75	87	100	125	150	187	225	250	312	500	–	–	–	–	–
45	44	55	66	77	88	111	133	166	200	222	277	444	555	–	–	–	–
50	40	50	60	70	80	100	120	150	180	200	250	400	500	–	–	–	–
55	36	45	54	63	72	90	109	136	163	181	227	263	454	545	–	–	–
60	30	41	50	58	66	83	100	125	150	166	208	333	416	500	–	–	–
65	–	38	46	53	61	76	100	115	138	153	192	307	384	461	538	–	–
70	–	35	42	50	57	71	85	107	128	142	178	285	357	428	500	–	–
75	–	–	40	46	53	66	80	100	120	133	166	266	333	400	466	666	–
80	–	–	37	43	50	62	75	93	112	125	156	250	312	375	437	625	–
85	–	–	–	41	47	58	70	88	105	117	147	235	294	352	411	588	–
90	–	–	–	38	44	55	66	83	100	111	138	222	277	333	388	555	1111
95	–	–	–	–	42	52	63	78	94	105	131	210	263	315	368	526	1052
100	–	–	–	–	40	50	60	75	90	100	125	200	250	300	350	500	1000

*DFT – Dry film thickness

Corrected volume solids after dilution Theoretical spreading rate (m2 | lt)

DFT* (µ)	Volume solids (%)
DFT* (µ)	20	25	30	35	40	45	50	55	60	65	70	75	80	85	90	95	100
20	10	12.5	15	17.5	20	22.5	25	27.5	30	32.5	35	37.5	40	42.5	45	47.5	50
25	8	10	12	14	16	18	20	22	24	26	28	30	32	34	36	38	40
30	6.7	8.3	10	11.7	13.3	15	16.7	18.3	20	21.7	23.3	25	26.7	28.3	30	31.7	33.3
50	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20
75	2.7	3.3	4	4.7	5.3	6	6.7	7.3	8	8.7	9.3	10	10.7	11.3	12	12.7	13.3
100	2	2.5	3	3.5	4	4.5	5	5.5	6	6.5	7	7.5	8	8.5	9	9.5	10
125	1.6	2	2.4	2.8	3.2	3.6	4	4.4	4.8	5.2	5.6	6	6.4	6.8	7.2	7.6	8
150	1.3	1.7	2	2.3	2.7	3	3.3	3.7	4	4.3	4.7	5	5.3	5.7	6	6.3	6.7
175	1.1	1.4	1.7	2	2.3	2.6	2.9	3.1	3.4	3.7	4	4.3	4.6	4.9	5.1	5.4	5.7
200	1	1.3	1.5	1.8	2	2.3	2.5	2.8	3	3.3	3.5	3.8	4	4.3	4.5	4.8	5
250	0.8	1	1.2	1.4	1.6	1.8	2	2.2	2.4	2.6	2.8	3	3.2	3.4	3.6	3.8	4
300	0.7	0.8	1	1.2	1.3	1.5	1.7	1.8	2	2.2	2.3	2.5	2.7	2.8	3	3.2	3.3
400	0.5	0.6	0.8	0.9	1	1.1	1.3	1.4	1.5	1.6	1.8	1.9	2	2.1	2.3	2.4	2.5
500	0.4	0.5	0.6	0.7	0.8	0.9	1	1.1	1.2	1.3	1.4	1.5	1.6	1.7	1.8	1.9	2

*DFT – Dry film thickness

Corrected volume solids after dilution

Original volume solids (%)	% of thinner added
Original volume solids (%)	5	10	15	20	25	33	50
15	14	13.6	13	12.5	12	11	10
20	19	18	17	16.7	16	15	13
25	24	23	22	21	20	19	17
30	29	27	26	25	24	23	20
35	33	32	30	29	28	26	23
40	38	36	35	33	32	30	27
45	43	41	39	37	36	34	30
50	48	45	43	42	40	38	33
55	52	50	48	46	44	41	37
60	57	55	52	50	48	45	40
65	62	59	56	54	52	49	43
70	67	64	61	58	56	53	47
75	71	68	65	62	60	56	50
80	76	73	70	67	64	60	53
85	81	77	74	71	68	64	57
90	86	82	78	75	72	68	60
95	90	86	83	79	76	71	63
100	95	91	87	83	80	75	67