Reduce it, split it,solve for the missing side.
A ratio is two numbers in a relationship, and most of the questions you actually have about one are simple math you shouldn't be doing by hand. Enter two values to simplify the ratio to its lowest terms, read it as a decimal and a clean percentage split, then solve a proportion when you know three of the four numbers.
Your numbers
The left side of the ratio — A in A:B.
The right side of the ratio — B in A:B.
Order matters: A:B is not the same relationship as B:A. The split below always reads A first.
The verdict
Simplified ratio
16 : 9
Decimal (A ÷ B)
1.8
A share
64.0%
B share
36.0%
The split, side by side
In plain words
Your ratio reduces to 16 : 9, a decimal of 1.7778. A owns 64.0% of the whole, B owns 36.0%.
Proportion · solve for the missing side
A : B = C : D
Keep the same relationship as your ratio above (16 : 9) and scale it. Pick which side you know, enter it, and the solver fills in the fourth number by cross-multiplying.
D (solved)
6.8
16 : 9 = 12 : 6.7500
Your move
The ratio is the easy part. Knowing which one to chase is the work.
16 : 9 simplifies cleanly — A holds 64.0% of the split, B holds 36.0%.
Plenty of teams track a budget split or an LTV:CAC ratio and still can't say whether it's the right one. Send me your numbers and I'll tell you which ratios actually move your business, what good looks like for your model, and where the current mix is quietly costing you. Free, and you keep the read whether you hire me or not.
Plain English
A ratio is a relationship, not a total.
A ratio compares two quantities — A to B — and tells you how big one is relative to the other. 16:9 means for every 16 units of width there are 9 of height. The numbers themselves rarely matter; what matters is the relationship between them, which is why 16:9, 32:18, and 1.78:1 all describe the same shape.
Simplifying a ratio means dividing both sides by their greatest common divisor until they share no common factor. 60:40 reduces to 3:2; 1920:1080 reduces to 16:9. The reduced form is the cleanest way to state the relationship and the easiest to recognize and compare against another.
From there, two readings make a ratio actionable. The decimal (A ÷ B) turns the relationship into a single number you can multiply or scale. The percentage split (A ÷ (A + B)) tells you what share of the whole each side owns — the right lens whenever the two parts add up to one budget, one audience, or one revenue pie.
The formula
Simplified A:B = (A ÷ gcd) : (B ÷ gcd) · Split = A ÷ (A + B)
Take 60:40. The greatest common divisor is 20, so it reduces to 3:2. As a decimal that's 60 ÷ 40 = 1.5. As a split it's 60 ÷ 100 = 60% to A and 40% to B. To solve a proportion, 3:2 = 12:? means ? = 2 × 12 ÷ 3 = 8.
What your ratio is actually telling you
The split is far from 50/50.
One side dominates. That's fine when it's intentional (a 70/30 brand-to-performance budget), but if it surprised you, it's usually a sign one input quietly grew without the other keeping pace. Check whether the imbalance is a decision or an accident.
The decimal is above 1.
A is larger than B. The further above 1, the more lopsided the relationship. A 4:1 ratio (decimal 4.0) means A is four times B — useful for sanity-checking things like LTV:CAC, where you want the first number comfortably bigger.
The decimal is below 1.
B is the larger side. Whenever you expected A to lead — leads to spend, output to input — a decimal under 1 is a flag that the relationship has inverted and the smaller number is doing the heavy lifting.
The simplified form is still ugly.
If A and B share no common factor, the ratio is already in lowest terms (e.g. 17:9). That's not an error — some relationships just don't reduce. Use the decimal or the percentage split when the reduced ratio isn't easy to read.
Where ratios earn their keep in marketing
01Budget splits
A 70:30 brand-to-performance ratio is a planning tool: state the split, hold it, and you stop relitigating the budget every quarter.
02LTV:CAC
The health ratio of acquisition. Aim for the first number to be several times the second; the decimal tells you at a glance whether you're above the line.
03Aspect ratios
16:9, 4:5, 1:1 — every placement has a shape. Simplify your asset's pixel dimensions to know which slots it fits without cropping.
04Test traffic allocation
Splitting an A/B test 50:50 maximizes power; an 80:20 split protects a control while you probe a risky variant. The ratio is the decision.
05Lead-to-customer
Stated as a ratio (say 12:1), your funnel's conversion becomes a target you can manage — and a yardstick for whether traffic or closing is the problem.
06Revenue mix
Express each channel or product as a share of the whole. The percentage split surfaces over-reliance on one source before it becomes a risk.
The vocabulary
- Ratio
- A comparison of two quantities, written A:B. It expresses relative size, not an absolute total.
- Simplified ratio
- A ratio reduced to its lowest terms by dividing both sides by their greatest common divisor.
- Greatest common divisor (GCD)
- The largest whole number that divides both values evenly. Dividing by it reduces the ratio.
- Proportion
- A statement that two ratios are equal, A:B = C:D. Knowing any three values lets you solve for the fourth.
- Percentage split
- Each side of a ratio expressed as a share of the total: A ÷ (A + B) and B ÷ (A + B).
- Decimal ratio
- A ratio written as a single number, A ÷ B. 3:2 becomes 1.5.
Ratio questions, straight answers
Divide both numbers by their greatest common divisor (the largest number that goes into both evenly), and repeat until they share no common factor. 60:40 has a GCD of 20, so it reduces to 3:2. This calculator does that automatically and shows the lowest-terms form the moment you type.
Keep going
A calculator tells you what. A call tells you what to do about it.
Send me the account behind these numbers. I'll tell you straight where the money's leaking and what I'd fix first — free, and you keep it whether you hire me or not.