Control Count
The control count is a supplementary method that is mainly used in combination with HCP count to determine the trick-taking potential of fitting hands, in particular to investigate slam potential. The use of control count addresses the fact that for suit contracts, aces and kings tend to be undervalued in the standard 4–3–2–1 HCP scale; aces and kings allow declarer better control over the hands and can prevent the opponents from retaining or gaining the lead.
The control count is the sum of the controls where aces are valued as two controls, kings as one control and queens and jacks as zero. This control count can be used as "tie-breakers" for hands evaluated as marginal by their HCP count. Hands with the same shape and the same HCP can have markedly different slam potential depending on the control count.
West: 
KJ632 
A2 
7543 
A5.
East: AQ985 K53 A6 K43
West: KJ632 A2 7543 A5.
East: AQ985 KQ3 Q6 K43
In the above examples, both West hands are the same, and both East hands have the same shape and HCP (16). Yet, the layout on the top represents a solid slam (12 tricks) in spades, whilst the layout on the bottom will fail to produce 12 tricks. The difference between the East hands becomes apparent when conducting a control count: in the top layout East has two aces and two kings for a total of six controls, whilst in the bottom layout has one ace and two kings for a total of four controls.
The interpretation of the significance of the control count is based upon a publication by George Rosenkranz in the December 1974 issue of The Bridge World 2001, page 144: EXPECTED NUMBER OF CONTROLS IN BALANCED HANDS. Rosenkranz defined "the expected number of controls in balanced hands" at specific HCP counts as 'control-neutral' in a table similar to the consolidation shown on the left; having more controls is deemed 'control-rich' and having less is 'control-weak'.
- 5 HCP - 1 expected control
- 7–8 HCP - 2 expected controls
- 10 HCP - 3 expected controls
- 12–13 HCP - 4 expected controls
- 15 HCP - 5 expected controls
- 17–18 HCP - 6 expected controls
- 20HCP - 7 expected controls
The table can be used as tie-breaker for estimating the slam-going potential of hands like the above two East hands. Whilst the top East hand counts 16 HCP, in terms of controls (6) it is equivalent to a hand typically 1–2 HCP stronger, whereas the bottom East hand, also counting 16 HCP, is in terms of controls (4) more equivalent to 12–13 HCP.
If West opens the bidding with 1, both East hands should aim for at least game 4, the partnership having the minimum 26 total points typically required for a game contract in the majors. Despite the spade suit fit, both East hands have marginal slam potential based on their 16 HCP count alone. On the top layout the control-rich East (an upgraded 17–18 HCP) should explore slam and be willing to bypass 4 in doing so, whilst on the bottom layout the control-weak East (a downgraded 12–13 HCP) should be more cautious and be prepared to stop in 4 spades should further bidding reveal West lacking a control in diamonds.
In his book "The Modern Losing Trick Count", Ron Klinger advocates the use of the control count to make adjustments to the LTC hand evaluation method.