SILDIL

Proportion Calculator

Solve proportions with a missing value, direct and inverse proportion, a proportionality checker, an equivalent-ratio generator, and a scale calculator for maps and models — with fraction and decimal input and a full step-by-step explanation.

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Proportion Type

Accepted formats: integers (2), decimals (2.5), or fractions (3/4). Leave exactly one field blank to solve for it.

First Ratio

Second Ratio

Result

Missing Value
Completed Proportion
Cross Product 1
Cross Product 2
Step-by-Step Solution

    How to Solve Proportions

    Step-by-step method to solve proportions, check equivalence, and convert scale measurements.

    1. 1. Choose a proportion type: Select basic, direct, inverse, check, equivalent ratios, or scale mode.
    2. 2. Enter your values: Input integers, decimals, or fractions. Leave exactly one field blank to solve for it.
    3. 3. Review the result: See the solved value, completed proportion, and cross products.
    4. 4. Follow the steps: Read the step-by-step explanation to understand how the answer was derived.

    What This Calculator Does

    • ✅ Basic Proportion: Solve A : B = C : D for any missing value using cross multiplication.
    • ✅ Direct Proportion: As one quantity increases, the other increases proportionally.
    • ✅ Inverse Proportion: As one quantity increases, the other decreases so the product stays constant.
    • ✅ Check Proportionality: Verify whether two ratios are equivalent.
    • ✅ Equivalent Ratios: Generate a list of ratios equal to a base ratio.
    • ✅ Scale: Convert map, model, or blueprint measurements to real-world distances.

    Enter fractions (e.g., 3/4) or decimals (e.g., 2.5) in any field. The calculator shows decimal answers and, where appropriate, converts back to fractions.

    Formulas

    • Direct Proportion: A / B = C / D → Cross multiply: A × D = B × C
    • Inverse Proportion: A × B = C × D (product is constant)
    • Scale: Real = Measurement × (Scale Real / Scale Map)
    • Equivalent Ratios: Multiply both terms by the same non-zero number.

    Examples

    • Basic: 2 : 5 = 8 : ? → Missing value = 20
    • Direct: 3 items cost $15. 7 items cost ? → $35
    • Inverse: 4 workers take 12 days. 6 workers take ? → 8 days
    • Check: Is 3 : 5 proportional to 12 : 20? → Yes
    • Equivalent: Base 3 : 5 → 6 : 10, 9 : 15, 12 : 20 …
    • Scale: Map scale 1 : 5 km. Map distance 7 cm → Real distance 35 km

    Frequently Asked Questions

    Q: What is a proportion?

    A proportion states that two ratios are equal. For example, 2 : 5 = 8 : 20 is a proportion because both ratios simplify to the same relationship.

    Q: How do you solve a proportion with a missing value?

    Leave one of the four values blank and enter the other three. The calculator uses cross multiplication to find the missing value and shows every step.

    Q: How do you cross multiply?

    For a proportion A : B = C : D, cross multiplication means A × D = B × C. If one value is unknown, you rearrange this equation to solve for it.

    Q: What is the difference between direct and inverse proportion?

    In direct proportion, as one quantity increases, the other increases at the same rate (A/B = C/D). In inverse proportion, as one quantity increases, the other decreases so that their product stays constant (A × B = C × D).

    Q: Can I enter fractions?

    Yes. Enter fractions in the format 3/4 or 1/2. The calculator converts them to decimals for computation and can convert answers back to fractions when appropriate.

    Q: What is an equivalent ratio?

    Equivalent ratios have the same simplified form. For example, 3 : 5, 6 : 10, and 9 : 15 are all equivalent because they all simplify to 3 : 5.

    Q: How does the scale proportion work?

    Enter a scale such as 1 : 5 (meaning 1 unit on a map or drawing equals 5 units in reality) and enter a measured value. The calculator finds the real-world equivalent.

    Q: Can proportions contain decimals?

    Yes. You can enter decimals such as 2.5 or 0.75 directly into any field.

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