Calculators
Electronics Calculators
The calculations that come up in every perfboard project, gathered in one place. Each calculator explains its formulas, working, and caveats, and accepts prefixes like 4.7k, 100n, and 2.2u as typed.
Calculator list
Resistor Color Code Calculator
Pick the color bands of a 4-band or 5-band resistor to get its value and tolerance, or enter a resistance to see the matching color bands.
LEDLED Resistor Calculator
Enter the supply voltage, LED forward voltage, and target current to calculate the current-limiting resistor, then see the actual current and heat when you switch to the nearest standard value.
OHMOhm's Law & Power Calculator
Know any two of voltage, current, resistance, and power and it calculates the other two. Prefixes like 4.7k and 100m can be typed in as they are.
DIVIDERVoltage Divider Calculator
Calculate the output voltage from the input voltage and resistors R1 and R2, and see how far the output drops when you connect a load resistance.
555555 Timer Calculator (Astable & Monostable)
Calculate the frequency, period, and duty cycle of an NE555 astable oscillator from R1, R2, and C, or the output time of a monostable (one-shot) from R and C.
RCRC Time Constant & Cutoff Frequency Calculator
Calculate the time constant τ, charge and discharge times, and the cutoff frequency of an RC low-pass filter from a resistor and capacitor value.
NETWORKSeries & Parallel Resistor Calculator
Calculate the combined resistance and current split of resistors connected in series or parallel. Handy for making a target value from two standard resistors.
Can you trust the calculators?
The calculators implement textbook formulas directly, and unit tests check each formula against representative examples. Real parts do have tolerances, though. Resistors are commonly off by ±1–5% and electrolytic capacitors by around ±20%, and LED forward voltage and 555 timing also vary from one product to the next. Use the results as a starting point for your design, and confirm the values that matter with a multimeter or oscilloscope.
If the concepts are unfamiliar, start with the principles in the guides. To try out a circuit you have calculated, check the voltages and currents with simulation in the editor.