Perimeter of a Triangle with Fractions Calculator
Add up three fractional (or mixed-number) side lengths to find the triangle's perimeter. Accepts any combination of proper fractions (3/4), improper fractions (5/3), mixed numbers (1 2/3), or decimals.
Enter each side as a fraction (e.g. 3/4), a mixed number (e.g. 1 2/3), or a decimal (e.g. 0.75).
a + b + c = 0.75 + 0.5 + 0.625
- 1
Convert side a to decimal
3/4 = 0.75 - 2
Convert side b to decimal
1/2 = 0.5 - 3
Convert side c to decimal
5/8 = 0.625 - 4
Perimeter = a + b + c
0.75 + 0.5 + 0.625 = 1.875000
How does this calculator work?
The perimeter of a triangle with fractional sides is just P = a + b + c, with each side converted to a common decimal. Enter sides as fractions (3/4), mixed numbers (1 2/3), or decimals; the calculator adds them, checks the triangle inequality, and shows each side's share of the total perimeter.
Formula
How this is calculated
The perimeter of a triangle is the sum of its three side lengths: P = a + b + c. When the sides are given as fractions, you add them by finding a common denominator, combining the numerators, and simplifying. For example, ¾ + ½ + ⅝ is computed by converting to eighths: 6/8 + 4/8 + 5/8 = 15/8 = 1⅞.
This calculator accepts each side as a fraction ("3/4"), a mixed number ("1 2/3", where a space separates the whole part from the fractional part), or a plain decimal ("0.75"). It converts each input to a decimal, sums them, and shows the result. The fraction bar below the result visualises how each side contributes to the total perimeter — useful for checking whether one side dominates.
The triangle inequality is enforced: a valid triangle requires that each side be strictly shorter than the sum of the other two. If the three sides cannot form a triangle, the calculator shows a warning rather than a meaningless sum.
Frequently asked questions
Find the least common denominator (LCD) of all fractions, convert each fraction to an equivalent one with that denominator, add the numerators, then simplify. For example, 1/2 + 1/3 = 3/6 + 2/6 = 5/6. This calculator does the arithmetic automatically — just enter the fractions and read off the decimal result.
Separate the whole part from the fractional part with a space: "1 2/3" means one and two-thirds. Do not use a plus sign or parentheses — just a space between the integer and the fraction.
The most likely reason is a violation of the triangle inequality: each side must be less than the sum of the other two. Sides of 1, 2, and 4, for example, cannot form a triangle because 1 + 2 = 3 < 4.
Also known as
TG we-Calculate Editorial Team. (2026). Perimeter of a Triangle with Fractions Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/perimeter-of-a-triangle-with-fractions-calculator
TG we-Calculate Editorial Team. "Perimeter of a Triangle with Fractions Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/perimeter-of-a-triangle-with-fractions-calculator.
TG we-Calculate Editorial Team, "Perimeter of a Triangle with Fractions Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/perimeter-of-a-triangle-with-fractions-calculator
@misc{wecalculate_perimeter_of_a_triangle_with_fractions_calculator, title = {Perimeter of a Triangle with Fractions Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/perimeter-of-a-triangle-with-fractions-calculator}}, year = {2026}, note = {TG we-Calculate} }
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