Introduction
Understanding betting odds can feel like decoding a secret language, especially when you encounter niche terms like “formula 43 odds.” In this guide, I’ll break down what the phrase can mean in practical betting contexts, how payout ratios are derived from various odds formats, and how to convert any set of odds into implied probability so you can make clearer, more disciplined decisions.
My aim is simple: if you search for formula 43 odds because you’re curious about payout ratio and implied probability, you’ll walk away knowing how to read, convert, and compare odds—without needing a PhD in math.
What Are “Formula 43 Odds”?
“Formula 43 odds” isn’t a universal industry label like decimal (1.50), fractional (2/1), or American (+150) odds. Instead, it typically appears in three scenarios:
- As shorthand in betting models or spreadsheets for a particular conversion approach—often a custom cell or a numbered formula step.
- As a colloquial tag for a rule-of-thumb method someone calls “Formula 43,” usually tied to a payout ratio or a probability conversion.
- As an internal reference in tip sheets or forums to denote a specific line-calculation routine.
For our purposes, I’ll use “formula 43 odds” to describe a practical, step-by-step way to convert odds to payout ratios and implied probabilities across formats. Think of it as a single workflow you can apply consistently.
The Core Building Blocks
Before we dive into the workflow, let’s anchor the definitions we’ll use throughout:
Decimal Odds
- Format: 1.60, 2.25, 3.40
- Payout (total return) = Stake × Decimal Odds
- Profit = Stake × (Decimal Odds − 1)
- Implied Probability = 1 ÷ Decimal Odds
Fractional Odds
- Format: 5/4, 9/2, 11/8
- Profit = Stake × (Numerator ÷ Denominator)
- Total Return = Stake + Profit
- Decimal Equivalent = (Numerator ÷ Denominator) + 1
- Implied Probability = Denominator ÷ (Numerator + Denominator)
American Odds
- Positive (e.g., +150): Profit = Stake × (Odds ÷ 100)
- Negative (e.g., −200): Profit = Stake × (100 ÷ |Odds|)
- Decimal Equivalent =
- For positive: (Odds ÷ 100) + 1
- For negative: (100 ÷ |Odds|) + 1
- Implied Probability =
- For positive: 100 ÷ (Odds + 100)
- For negative: |Odds| ÷ (|Odds| + 100)
Payout Ratio
- Also called the “odds multiplier” or “return multiple.”
- Defined as Total Return ÷ Stake.
- For decimal odds, it’s literally the odds value (e.g., 2.25 means a 2.25× return on stake).
Implied Probability
- The probability of success implied by the offered odds, ignoring bookmaker margin (vig).
- If you sum implied probabilities of all mutually exclusive outcomes in a market and get more than 100%, the excess is the overround (the book’s margin).
The “Formula 43” Workflow (Odds → Payout Ratio → Implied Probability)
I like to keep a single, compact workflow that works no matter where I start:
Step 1: Normalize to Decimal Odds
- If you have fractional odds a/b: Decimal = (a ÷ b) + 1
- If you have American odds:
- Positive +X: Decimal = (X ÷ 100) + 1
- Negative −Y: Decimal = (100 ÷ Y) + 1
Why normalize? Because decimal odds directly represent the payout ratio (return multiple), which simplifies downstream math.
Step 2: Read the Payout Ratio
- Payout Ratio = Decimal Odds
- Profit Multiple = Decimal Odds − 1
This tells you how many units you get back per unit staked, including your stake.
Step 3: Convert to Implied Probability
- Implied Probability = 1 ÷ Decimal Odds
- As a percentage: Probability% = (1 ÷ Decimal Odds) × 100
Now you have a clean, comparable probability view.
Worked Examples
Example 1: Fractional 9/4
- Decimal = (9 ÷ 4) + 1 = 3.25
- Payout Ratio = 3.25×
- Implied Probability = 1 ÷ 3.25 ≈ 0.3077 → 30.77%
Example 2: American +150
- Decimal = (150 ÷ 100) + 1 = 2.50
- Payout Ratio = 2.50×
- Implied Probability = 1 ÷ 2.50 = 0.40 → 40%
Example 3: American −200
- Decimal = (100 ÷ 200) + 1 = 1.50
- Payout Ratio = 1.50×
- Implied Probability = 1 ÷ 1.50 ≈ 0.6667 → 66.67%
Example 4: Fractional 5/6
- Decimal = (5 ÷ 6) + 1 ≈ 1.8333
- Payout Ratio ≈ 1.8333×
- Implied Probability ≈ 1 ÷ 1.8333 ≈ 0.5455 → 54.55%
How to Handle Bookmaker Margin (Overround)
Real markets have vig. If you want “true odds,” you can deflate the implied probabilities to remove the margin.
Step 1: Get each outcome’s implied probability
- Use 1 ÷ Decimal for each outcome.
Step 2: Sum them to find the overround
- Overround = Sum(Implied Probabilities)
- If the market were perfectly fair, the sum would be 1 (or 100%). Anything above that is the margin.
Step 3: Deflate to get no-vig probabilities
- No‑Vig Probability for outcome i = (Implied Pi) ÷ Overround
Step 4: Convert back to odds if needed
- No‑Vig Decimal Odds = 1 ÷ No‑Vig Probability
This gives you a cleaner comparison baseline across bookmakers.
Payout Ratio vs. Profit: Don’t Confuse Them
- Payout (or return) includes your stake; profit does not.
- If Decimal = 2.10, a 100-unit stake returns 210 units (payout ratio 2.10×) and profits 110 units.
- Always check whether a calculator or article quotes payout or profit; the difference can mislead bankroll planning.
Quick Reference: Conversions at a Glance
From Decimal Odds d
- Payout Ratio = d
- Profit Multiple = d − 1
- Implied Probability = 1/d
From Fractional a/b
- Decimal = (a/b) + 1
- Payout Ratio = (a/b) + 1
- Implied Probability = b/(a + b)
From American +X or −Y
- Decimal =
- If +X: (X/100) + 1
- If −Y: (100/Y) + 1
- Payout Ratio = Decimal
- Implied Probability =
- If +X: 100/(X + 100)
- If −Y: Y/(Y + 100)
Applying “Formula 43” to Real Betting Decisions
1) Compare Lines Across Books
Normalize to decimal, compute implied probability, and pick the best price (lowest implied probability for the same outcome). That’s effectively finding the highest payout for the same bet.
2) Sanity‑Check Your Model
If your own estimated win probability (say, 44%) exceeds the no‑vig implied probability (say, 40%), there’s theoretical value. If it’s lower, pass.
3) Manage Bankroll Using Edge‑Aware Stakes
Use Kelly fraction or a fixed‑fraction method based on your perceived edge. A conservative approach is half‑Kelly to reduce risk of drawdowns.
- Kelly fraction (for decimal odds d and edge p): f* = (p×d − 1)/(d − 1)
- For American odds, convert to decimal first; for fractional, same idea.
4) Track Closing Line Value (CLV)
If the decimal odds you took are consistently higher than the market’s closing odds, your process is finding value—even if short‑term results fluctuate.
Common Mistakes to Avoid
Mixing Up Formats Mid‑Calculation
Convert once at the start. Don’t bounce between fractional and American midstream.
Forgetting the Stake in Payouts
Profit is not payout. Your bankroll planning depends on this distinction.
Ignoring Vig
Raw implied probabilities are inflated by the margin. Adjust to no‑vig for apples‑to‑apples comparisons.
Overfitting Tiny Edges
A nominal edge (e.g., 0.5%) evaporates with small errors in your model and line movement. Demand a buffer.
Building Your Own “Formula 43” Sheet
Recommended Columns
- Input Odds (original format)
- Normalized Decimal
- Payout Ratio (Return Multiple)
- Implied Probability
- No‑Vig Implied Probability (optional)
- Edge vs. Your Model
- Stake Size (method of choice)
Basic Cell Formulas
- Decimal from fractional (a in A2, b in B2): =A2/B2 + 1
- Decimal from American (X in C2): =IF(C2>0, C2/100+1, 100/ABS(C2)+1)
- Implied Probability (decimal in D2): =1/D2
- No‑Vig Probability (E2 implied, sum in S2): =E2/$S$2
- Kelly fraction (decimal in D2, est. prob in P2): =(P2*D2-1)/(D2-1)
Frequently Asked Questions
Is there a single “best” odds format?
Not really. Decimal is cleanest for math; American is popular in the U.S.; fractional remains common in horse racing. Normalize and you’re fine.
What payout ratio is “good”?
There isn’t an absolute “good.” It depends on the true probability. A 5.00 payout ratio is fantastic if the true win chance exceeds 20%; otherwise, it’s a bad bet.
Can I skip the no‑vig step?
You can for quick checks, but you’ll misjudge value around tight markets. For serious betting, at least sanity‑check with no‑vig.
Conclusion
When someone references “formula 43 odds,” they’re often pointing at a practical routine for turning odds into payout ratios and implied probabilities. By normalizing to decimal, reading the payout multiple, and converting to implied probability—then adjusting for vig—you get a consistent, sharable framework for line shopping, bankroll sizing, and long‑term discipline.
Once you’ve practiced the workflow a few times, it becomes muscle memory. Your analysis gets faster, your comparisons cleaner, and your decisions calmer—exactly what you want when numbers are moving and time is short.
