Arithmetic & Algebra Calculators
Calculators, percentages, fractions, ratios, powers and logs, quadratics and linear systems.
Calculators
- Basic Calculator
Arithmetic with keyboard input, exact decimals and clear operator precedence.
- Scientific Calculator
Trig, logs, powers and roots in degrees or radians with visible precedence.
- Percentage Calculator
Percent of a number, reverse percentages and percentage change.
- Fraction Calculator
Exact fraction arithmetic with simplification and mixed numbers.
- Ratio and Proportion Calculator
Simplify ratios, solve proportions for a missing value and scale ratios.
- Exponent, Root and Logarithm Calculator
Powers, nth roots and logarithms in any base with domain checks.
- Quadratic Equation Solver
Real, repeated or complex roots of ax² + bx + c = 0, with the discriminant and vertex.
- System of Linear Equations Solver
Solve 2×2 and 3×3 systems and detect singular or inconsistent systems.
Which arithmetic or algebra calculator to use
A keypad handles anything you can type as an expression. A dedicated calculator adds the method, and explains the cases a keypad gets wrong or leaves as a bare error.
- Plain arithmetic, or a formula with functions?
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Basic Calculator Scientific Calculator
Exact decimal arithmetic for everyday sums, or trigonometry, logarithms and powers with the way your expression was read shown back to you.
- Percent of, percent change or percentage points?
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Each common percentage question as its own mode, with the formula it used.
- Fractions or mixed numbers?
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Exact answers in lowest terms, as a mixed number and as a decimal with any repeating digits marked.
- Scaling, or sharing something out in a ratio?
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Ratio and Proportion Calculator
Simplifies ratios, solves a proportion for the missing term and divides a total in a given ratio.
- Powers, roots or logarithms?
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Exponent, Root and Logarithm Calculator
Results with the rule applied, and a plain explanation when an input is outside the domain.
- Solving an equation?
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Quadratic Equation Solver System of Linear Equations Solver
Real or complex roots of a quadratic with its vertex and graph; two or three linear equations solved exactly, including the no-solution and infinitely-many cases.
Have these to hand
- Exact values where you have them. Fractions typed as fractions stay exact all the way through.
Mistakes that change the answer
- Calling a rise from 4% to 5% a 1% increase. It is one percentage point, and a 25% increase.
- Typing −3² and expecting 9. By convention the power applies first, giving −9.
- Rounding intermediate results before the final step.
- Working in degrees when the problem is stated in radians, or the reverse.
Related guides
- Common percentage mistakes and how to avoid them
Six percentage slips that produce confident wrong answers, from percentage points to negative starting values, each worked with example numbers you can check.
- Unit conversion pitfalls: gallons, tons, cups, GB vs. GiB
Nine unit traps with the numbers worked out: US vs. imperial gallons and pints, fluid ounces vs. ounces, three kinds of ton, cups of flour in grams, cup and tablespoon sizes, GB vs. GiB, bits vs. bytes, temperature changes and UK vs. US mpg.
- Solving triangles: which rule to use, and the SSA ambiguous case
A table for choosing the law of sines or the law of cosines, a worked SSA example with two valid answers, and the step-order and rounding traps that make hand-solved triangles go wrong.
- Margin vs. markup: formulas, conversion chart and discounts
Margin and markup divide the same profit by different numbers. How to convert one to the other, set a price for a target margin, and work out what a discount really costs.
- Mean, median or mode? How to choose a summary statistic
How to pick the center and spread that describe your data fairly, with worked numbers and a side-by-side of the quartile rules that different tools use.
- How to measure a room for square footage and volume
Measure, convert inches to decimal feet, split odd shapes into rectangles, then multiply and convert with a squared or cubed factor. Worked with an L-shaped room, a concrete pad and a water tank.