What is Deck Clocking?
Deck clocking is a technique used to mentally identify a missing card from a deck. By quickly scanning through the visible cards and performing mental arithmetic, a skilled practitioner can determine which card has been removed.
This app helps you practice and improve your speed at clocking a deck by timing your attempts and providing immediate feedback.
The Math Behind Clocking
Each card has a numerical value:
| Card | Value |
|---|---|
| Ace | 1 |
| 2 - 10 | Face value |
| Jack | 1 |
| Queen | 2 |
| King | 3 |
As you scan the cards, sum their values and keep only the ones digit (e.g., 47 becomes 7). The final digit tells you the missing card's rank:
| Result | Missing Card |
|---|---|
| 0 | 10 |
| 1 | Ace or Jack |
| 2 | 2 or Queen |
| 3 | 3 or King |
| 4 - 9 | That number |
For results of 1, 2, or 3, scan back through the cards to see which possibility is missing.
Settings
Color
Choose which color card will be hidden (the "clocked" card).
Deck
Choose how many cards to display during the drill.
Full Deck: Shows 51 cards (entire deck minus the hidden card).
Half: Shows only the 25 cards of your selected color (useful for beginners or faster practice).
Direction of Scroll
Choose which direction to scroll through the card spread.
R to L (Right to Left): Cards start on the right, mimicking how a deck is typically fanned from the left hand. This is the traditional method.
L to R (Left to Right): Cards start on the left for standard left-to-right scrolling.
How to Use
- Configure your settings on the home screen and tap Start.
- The timer begins immediately. Swipe through the cards to scan and mentally calculate the missing card.
- Tap Done when you've identified the missing card. The timer stops.
- Scroll back if needed to verify your answer, then tap Reveal.
- Check your answer against the revealed card and note your time.
- Tap Play Again to start a new drill.
Tip: Use the "Restart" button during a drill to return to the settings screen and try different options.
Drill Mode
Drill Mode is a 1-minute speed quiz to sharpen your clocking math. Instead of scanning a full spread, you're shown a small fan of cards and must quickly tap the ones digit of their combined clocking value. The goal is to answer as many correctly as possible before the timer runs out.
Tap Drill Mode on the home screen to access it.
Drill Mode Settings
Mix
Choose which cards appear in each question.
Face Cards: Questions use only Jacks, Queens, Kings, and Aces — the cards most likely to trip you up since they don't equal their face value.
All Cards: Questions draw from the full deck for a broader challenge.
Color
Choose which color of cards to drill on.
How to Use Drill Mode
- Configure your settings on the Drill Mode screen and tap Start.
- The 60-second timer begins. A fan of cards is shown — sum their clocking values and tap the ones digit on the keypad.
- Instant feedback: The key you tapped flashes green for correct, red for incorrect. A new hand is dealt immediately.
- When time runs out, your final correct count is displayed. Tap Play Again to try again or Home to return to the main screen.
Tip: The timer turns red when 10 seconds remain. Use the "Restart" button mid-drill to go back to settings.
Tips for Improvement
Start with Half Deck: Begin with the Half setting to practice with fewer cards before graduating to a full deck.
Practice the math: The faster you can add card values and reduce to a single digit, the quicker you'll clock the deck.
Develop a rhythm: Try to scan cards at a consistent pace rather than rushing and making mistakes.
Track your times: Note your times mentally or on paper to track your improvement over multiple sessions.