# What is the antilog of a number?

Raises a base to a logarithm to find the original number, or finds the log value or the base from the other two.

- Page: https://www.acalculator.org/math/antilog-calculator
- JSON spec: https://www.acalculator.org/math/antilog-calculator.json
- Version: 2c6090c75277

## Default answer

Example with the default inputs (Base (b) 10, Log value (y) 2): The antilog of 2 in base 10 is 100.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| b | Base (b) | The base of the logarithm: 10 for the common antilog, 2.718281828 (e) for the natural one. |
| logValue | Log value (y) | The logarithm to turn back into a number. |
| answer | Antilog (x) | The number whose logarithm in this base is the log value: the base raised to the log value. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| base | Base (b) | The base of the logarithm: 10 for the common antilog, 2.718281828 (e) for the natural one. |
| logValue | Log value (y) | The logarithm to turn back into a number. |
| antilog | Antilog (x) | The number whose logarithm in this base is the log value: the base raised to the log value. |

## Method

x = antilog_b y = b^y, so log_b x = y.

## Assumptions

- The base is more than 0 and not 1, so the antilog is always more than 0.
- An old link with base=e uses Euler’s number e ≈ 2.718281828 as the base.
- A whole-number log value or base within float error is shown exactly.

## Worked examples

1. b = 10, logValue = 2 gives answer = 100. Source: OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions.
2. b = 2, logValue = 10 gives answer = 1,024. Source: OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions.
3. b = 10, logValue = -2 gives answer = 0.01. Source: OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions.
4. b = 10, logValue = 0.5 gives answer = 3.162278. Source: OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions.
5. b = 2.718282, logValue = 1 gives answer = 2.718282. Source: OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions.
6. b = 10, answer = 1,000 gives logValue = 3. Source: OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions.
7. logValue = 2, answer = 49 gives b = 7. Source: OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions.

## FAQ

### What is an antilogarithm and how does it work?

An antilogarithm (antilog) is the inverse operation of a logarithm. It answers the question: 'What number do I get when I raise the base to a given power?' For example, antilog₁₀(2) = 100 because 10² = 100. The general form is antilogₐ(b) = c, which means aᵇ = c. Antilogarithms are essential for converting logarithmic results back to their original values and are widely used in scientific calculations, signal processing, and data analysis.

### What are the most common types of antilogarithms?

The three most common types are: 1) Common antilogarithm (antilog₁₀ or 10ˣ) - uses base 10, widely used in scientific notation and pH calculations; 2) Natural antilogarithm (eˣ or exp(x)) - uses base e (≈2.71828), fundamental in calculus and mathematical analysis; 3) Binary antilogarithm (2ˣ) - uses base 2, important in computer science and information theory. Each has specific applications where it's most useful.

### How do I convert between different antilogarithm bases?

You can convert between antilogarithm bases using the relationship: antilogₐ(b) = antilogᵤ(b × logᵤ(a)), where u is any positive number. For example, to convert antilog₂(3) to base 10: antilog₂(3) = 10^(3 × log₁₀(2)) = 10^(3 × 0.3010) = 10^0.9031 = 8. This conversion is useful when you need to work with different bases in calculations.

### What are the key properties of antilogarithms?

Key antilogarithmic properties include: 1) antilogₐ(0) = 1 (any base to power 0 equals 1); 2) antilogₐ(1) = a (base to power 1 equals itself); 3) antilogₐ(x + y) = antilogₐ(x) × antilogₐ(y) (product rule); 4) antilogₐ(x - y) = antilogₐ(x) ÷ antilogₐ(y) (quotient rule); 5) antilogₐ(nx) = (antilogₐ(x))ⁿ (power rule). These properties make antilogarithms powerful tools for simplifying complex mathematical expressions.

### Why can't antilogarithms have negative bases?

Antilogarithms cannot have negative bases because raising a negative number to a non-integer power results in complex numbers, which are not always meaningful in real-world applications. For example, (-2)^(1/2) = √(-2) = i√2, which is a complex number. The domain of antilogₐ(x) requires a > 0 and a ≠ 1 for meaningful real results. This is why calculators return errors when you try to compute antilogarithms with negative bases.

### What is the relationship between antilogarithms and exponential functions?

Antilogarithms and exponential functions are essentially the same operation. If y = antilogₐ(x), then y = aˣ. This means antilogarithms are exponential functions: antilogₐ(x) = aˣ. For example, antilog₁₀(3) = 10³ = 1000. This relationship is fundamental in solving exponential equations and modeling growth/decay processes in science and finance.

### How are antilogarithms used in real-world applications?

Antilogarithms have numerous real-world applications: 1) Converting pH back to hydrogen ion concentration ([H⁺] = 10^(-pH)); 2) Converting decibel measurements back to sound intensity; 3) Compound interest and financial growth calculations; 4) Population growth modeling; 5) Signal processing and audio engineering; 6) Scientific notation conversions; 7) Algorithm complexity analysis in computer science. They're essential for understanding phenomena that span many orders of magnitude.

### What's the difference between eˣ and 10ˣ?

eˣ is the natural antilogarithm (base e ≈ 2.71828), while 10ˣ is the common antilogarithm (base 10). The natural antilogarithm is fundamental in calculus and mathematical analysis because the derivative of eˣ is eˣ, making it essential for solving differential equations. Common antilogarithms are more intuitive for human-scale calculations since we use base-10 number systems and scientific notation.

### How do I solve antilogarithmic equations?

To solve antilogarithmic equations, use these strategies: 1) Use the exponential relationship: if antilogₐ(x) = b, then aˣ = b; 2) Apply logarithmic properties to both sides when needed; 3) Convert to logarithmic form when possible; 4) Check for extraneous solutions. For example, to solve antilog₂(x) = 8, convert to 2ˣ = 8, then x = 3 since 2³ = 8.

### What are exponential scales and why are they useful?

Exponential scales represent data where values grow by multiplication rather than addition. On an exponential scale, equal distances represent equal ratios rather than equal differences. They're useful for: 1) Visualizing data that grows exponentially; 2) Comparing relative growth rates; 3) Making large ranges of values visible on the same graph; 4) Identifying patterns in multiplicative relationships. Common examples include population growth charts and compound interest graphs.

### How do antilogarithms relate to the concept of exponential growth and decay?

Antilogarithms are fundamental to modeling exponential growth and decay. Growth models use the form N(t) = N₀ × e^(rt) where e^(rt) is the natural antilogarithm. Decay models use N(t) = N₀ × e^(-rt). These models describe phenomena like population growth, radioactive decay, compound interest, and temperature changes. The antilogarithm function eˣ is essential for solving these differential equations and understanding the underlying mathematical relationships.

### What are the historical origins of antilogarithms?

Antilogarithms were developed alongside logarithms by Scottish mathematician John Napier in 1614. While logarithms convert multiplication to addition, antilogarithms convert addition back to multiplication. This made it possible to perform complex calculations using slide rules and logarithm tables. The invention revolutionized navigation, astronomy, and engineering by providing a way to reverse logarithmic calculations and find original values from logarithmic results.

### How do antilogarithms appear in calculus and mathematical analysis?

Antilogarithms are crucial in calculus: 1) The derivative of eˣ is eˣ, making it, up to a constant multiple, the only function equal to its own derivative; 2) The integral of eˣ is eˣ + C; 3) They're used in solving differential equations and modeling growth/decay; 4) The natural antilogarithm appears in Taylor series expansions; 5) They're essential for Laplace transforms and Fourier analysis. This makes eˣ one of the most important functions in mathematical analysis.

## Sources

- OpenStax, College Algebra 2e, §6.3 Logarithmic Functions. https://openstax.org/books/college-algebra-2e/pages/6-3-logarithmic-functions
- NIST Digital Library of Mathematical Functions, §4.2 Definitions (logarithm, exponential, powers). https://dlmf.nist.gov/4.2