Note 6 - Investments in Joint Ventures - Condensed Income Statement of EXCOR and All Other Joint Ventures (Details) - USD ($)	3 Months Ended		6 Months Ended
	Feb. 28, 2023	Feb. 28, 2022	Feb. 28, 2023	Feb. 28, 2022
Net sales	$ 18,270,825	$ 16,748,639	$ 38,223,591	$ 34,942,052
Gross profit	6,403,186	4,984,335	12,756,310	10,687,265
Net income	885,248	182,847	1,387,490	4,676,606
Northern Technologies International Corporation’s share of equity in income from joint ventures	1,128,731	922,832	2,318,135	2,297,581
EXCOR and All Other Joint Venturs [Member]
Northern Technologies International Corporation’s share of equity in income from joint ventures	1,128,731	922,832	2,318,135	2,297,581
Northern Technologies International Corporation's dividends received from joint ventures	422,048	320,365	3,464,736	5,362,636
EXCOR [Member]
Northern Technologies International Corporation’s share of equity in income from joint ventures	676,800	589,048	1,547,944	1,499,821
Northern Technologies International Corporation's dividends received from joint ventures	0	0	2,459,500	4,255,200
All Other [Member]
Northern Technologies International Corporation’s share of equity in income from joint ventures	451,931	333,784	770,191	797,760
Northern Technologies International Corporation's dividends received from joint ventures	422,048	320,365	1,005,236	1,107,436
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Net sales	25,482,590	24,601,767	50,212,879	51,624,762
Gross profit	10,035,811	9,845,002	19,729,379	20,877,961
Net income	1,969,046	1,851,591	4,615,954	4,629,196
EXCOR [Member]
Net sales	9,708,482	9,312,434	19,854,403	20,612,662
Gross profit	4,733,435	4,658,450	9,453,477	10,127,436
Net income	1,365,170	1,170,187	3,107,457	2,991,734
All Other [Member]
Net sales	15,774,108		30,358,476	31,012,100
Gross profit	5,302,376		10,275,902	10,750,525
Net income	$ 603,876		$ 1,508,497	$ 1,637,462
Joint Ventures in France [Member]
Net sales		15,289,333
Gross profit		5,186,552
Net income		$ 681,404