Circle Diameter & Omtrek Calculator
Quickly calculate omtrek (circumference) from diameter, or calculate diameter from omtrek. Enter one value, choose your mode, and click calculate.
What is the relationship between diameter and omtrek?
The diameter and omtrek of a circle are directly connected by one of the most famous constants in mathematics: pi (π). If you know the diameter, you can always find the omtrek. If you know the omtrek, you can work backward to find the diameter.
In Dutch, omtrek means the total distance around a shape. For a circle, that is the same concept as circumference. This makes a diameter omtrek calculator useful for school math, engineering, DIY projects, and day-to-day measurements.
Core formulas used in this calculator
1) Diameter to omtrek
Omtrek = π × Diameter
Example: if the diameter is 10 cm, then the omtrek is approximately 31.42 cm.
2) Omtrek to diameter
Diameter = Omtrek ÷ π
Example: if the omtrek is 94.2 cm, then the diameter is approximately 30 cm.
How to use the diameter omtrek calculator
- Select whether you want to calculate omtrek from diameter or diameter from omtrek.
- Enter your known value as a positive number.
- Optionally add a unit such as mm, cm, m, inch, or feet.
- Choose a pi precision level depending on the accuracy you need.
- Click Calculate to get the result instantly.
When this tool is useful
Home improvement and DIY
Measuring round tables, rugs, pipes, lids, or circular cutouts often starts with a diameter. Converting to omtrek helps you estimate trim, edging, tape length, or material needed around the outside.
School and homework
Students frequently practice circle geometry. This calculator helps verify answers and understand how formulas behave as values get bigger or smaller.
Manufacturing and design
In technical work, you may know a wheel, gear, or cylinder diameter but need the perimeter distance for belt sizing, labeling, or rotational calculations.
Tips for accurate results
- Use consistent units from start to finish.
- Measure diameter through the center of the circle, not near the edge.
- Use more decimal places of π when precision matters.
- Round only at the end of your calculation.
Quick reference
- If diameter doubles, omtrek also doubles.
- If omtrek is known, divide by π to get diameter.
- Radius is always half the diameter.
Frequently asked questions
Is omtrek the same as circumference?
Yes. For circles, omtrek and circumference both mean the distance around the circle.
Can I use comma decimals?
Yes. You can enter values like 12,5 and the calculator will interpret them correctly.
What unit should I use?
Any unit works as long as you stay consistent. If you enter diameter in cm, the output will also be in cm.
Final thoughts
A good diameter omtrek calculator saves time and avoids mistakes. Whether you call it omtrek berekenen, diameter berekenen, or a circle circumference tool, the logic is simple and powerful: multiply by π to go from diameter to omtrek, divide by π to go the other way.