Resistance Converter
Convert electrical resistance between ohms, kilohms, megohms, milliohms, abohms, statohms, and siemens with color code display.
Resistance Converter
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Formula: R (ohms) = V / I | Conductance (S) = 1 / R | Converted = Input x (From Factor / To Factor)
Worked example โ 4.7 kohm = 4700 ohms = 0.0047 Mohm
Formula
R (ohms) = V / I | Conductance (S) = 1 / R | Converted = Input x (From Factor / To Factor)
Resistance conversion uses the ohm as the base SI unit. All metric resistance units convert through standard SI prefixes. The siemens (conductance) is the reciprocal of resistance. CGS units relate through electromagnetic (abohm = 1 nanoohm) and electrostatic (statohm = 8.988 x 10^11 ohm) conversion factors.
Worked Examples
Example 1: Resistor Value Conversion
Problem:A circuit diagram specifies a 4.7 kilohm resistor. Express this in ohms and megohms.
Solution:4.7 kohm to ohms: 4.7 x 1000 = 4700 ohms 4.7 kohm to Mohm: 4.7 / 1000 = 0.0047 Mohm Conductance: 1/4700 = 0.000213 S = 0.213 mS 4.7k is a standard E24 resistor value.
Result:4.7 kohm = 4700 ohms = 0.0047 Mohm
Example 2: Wire Resistance Measurement
Problem:A copper wire measures 50 milliohms resistance. Convert to ohms and microhms.
Solution:50 mohm to ohms: 50 x 0.001 = 0.05 ohms 50 mohm to uohm: 50 x 1000 = 50,000 uohm This low resistance is typical for short lengths of heavy gauge wire.
Result:50 mohm = 0.05 ohms = 50,000 uohm
Frequently Asked Questions
What is electrical resistance and what is an ohm?
Electrical resistance is the opposition to the flow of electric current in a conductor. The ohm is the SI unit of resistance, defined as the resistance between two points when a constant potential difference of one volt produces a current of one ampere (R = V/I). It is named after German physicist Georg Simon Ohm who formulated Ohm Law. Resistance depends on the material resistivity, length, and cross-sectional area of the conductor.
How do I read resistor color codes?
Standard 4-band resistor color codes use the first two bands for significant digits, the third band for the multiplier (number of zeros), and the fourth band for tolerance. The colors represent digits 0-9: Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Gray=8, White=9. For example, Brown-Black-Red-Gold means 10 x 100 = 1000 ohms (1 kilohm) with 5% tolerance. Resistance Converter shows approximate color bands for your resistance value.
What is the relationship between resistance and conductance?
Conductance is the reciprocal (inverse) of resistance. The SI unit of conductance is the siemens (S), formerly called the mho. If a resistor has 1000 ohms of resistance, its conductance is 1/1000 = 0.001 siemens or 1 millisiemens. High resistance means low conductance and vice versa. Conductance is useful in parallel circuit analysis and in describing the behavior of semiconductors and electrolytic solutions.
What are abohm and statohm units?
The abohm and statohm are CGS system units of resistance. One abohm equals one nanoohm (10^-9 ohm) and belongs to the electromagnetic CGS (EMU) system. The statohm is enormously large, approximately 8.988 x 10^11 ohms, from the electrostatic CGS (ESU) system. These units are historical and rarely used in modern engineering, but they appear in older physics literature and some theoretical electromagnetic calculations.
How does Ohm law connect resistance, voltage and current?
Ohm law states that resistance equals voltage divided by current, R = V / I, which is why the ohm is also expressible as one volt per ampere. Rearranged it gives V = IR for the drop across a resistor and I = V / R for the current a supply pushes through it. Power dissipation follows as P = I squared times R, which sets the wattage rating a resistor must survive.
What is resistivity and how does it differ from resistance?
Resistivity is a material property measured in ohm metres, while resistance is a property of a specific object. They connect through R = rho x L / A, so a conductor gets more resistive as it lengthens and less resistive as its cross section grows. Copper and aluminium have low resistivity, nichrome and carbon much higher, which is why heating elements and resistors are not made from copper.
How does temperature affect a resistor value?
Most metals have a positive temperature coefficient, so their resistance rises as they heat, while carbon composition and many semiconductors fall. The coefficient is quoted in parts per million per degree, and precision circuits use low-coefficient alloys to keep drift small. Thermistors exploit the effect deliberately, with negative-coefficient types dropping sharply with temperature so that resistance itself becomes the temperature reading.
How do resistances combine in series and in parallel?
In series the resistances simply add, so the total always exceeds the largest element. In parallel the reciprocals add, meaning the total conductance in siemens is the sum of the individual conductances and the resulting resistance is always smaller than the smallest branch. Two equal resistors in parallel give half the value, a common way to reach values outside the standard series.
What is sheet resistance and why is it quoted in ohms per square?
Sheet resistance describes a thin conductive film of uniform thickness. Because resistance depends on length divided by width for a film of fixed thickness, any square patch has the same resistance regardless of its size, so the unit is written as ohms per square. Thick-film resistors, printed traces and transparent conductive coatings are specified this way, and a trace resistance is the sheet value times the number of squares.
When should a value be written in kilohms rather than ohms or megohms?
Engineering practice keeps the significant figures between one and about three digits by stepping the prefix in factors of one thousand, so 4,700 ohms becomes 4.7 kilohms and 2,200,000 ohms becomes 2.2 megohms. Standard component values follow the E-series, which is why 4.7 and 2.2 appear so often. Consistent prefixes also reduce decimal-point errors when a schematic is read quickly.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator ยท Editorial policy
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