The Suit Quality Test for Overcalls

A measure of suit quality is to add together the number of honour cards, plus the suit length.

Honour cards are A,K,Q. Only count a J as an honour if it is supported by higher honour card in the same long suit. Count the 10 as an honour if the J and a higher honour card is present in the suit

Assuming you have adequate high card points, an overcall requires having a suit qualty value of at least the level of the overcall. (the old adage is "do not overcall in a suit you would not want led"). Overcalling on suits such as J97532 is bad unless you win the contract!

Examples: a suit of AJ984 has a SQ of 7 (2 honours+5 card suit), so is good enough to overcall at the 1 level but NOT the 2 level. With a better than minimum hand you may still decide to overcall at the 2 level. A suit of 10987643 is not good enough to overcall at the 2 level (at favourable vulnerability you may make a weak jump overcall pre-emptively). A similar 7 card suit headed by the Ace qualifies for a 2 level overcall with adequate outside strength and favourable vulnerability.

Is your suit good enough to insist as the trump suit? With a SQ value of 10 or more it is! Holding a suit of AKJ1075, this suit has a SQ value of 10 (6 card suit+4 'honour' cards), so you should insist this is the trump suit. You are unlikely to lose more than 1 trick in the suit