Resistor calculator: SMD & LED

Turn resistor markings into useful circuit values. Resistor calculator helps electronics students, hobbyists and makers read color bands, decode SMD codes and work through everyday component calculations in one workbench. READ COLOR BANDS AND SMD CODES Select the colors on a 3, 4, 5 or 6-band resistor to find nominal resistance and its tolerance range. Six-band decoding also shows the temperature coefficient. A built-in reference explains band meanings, while the value-to-color tool works in reverse: enter a resistance and tolerance to see a supported four or five-band pattern. Type a surface-mount resistor marking instead of searching through tables. Decode three or four-digit codes, decimal-letter markings and supported EIA-96 codes. Try examples such as 103 or 4R7, select a marking system when a code is ambiguous, and choose a resistance display unit. CHOOSE VALUES FOR YOUR CIRCUIT - Series and parallel: add or remove resistors, choose their units and calculate the equivalent resistance of the selected connection. - Standard resistor finder: compare nearby E12, E24 and E96 nominal values, including their percentage difference from your target. - Combination finder: search for two standard resistors connected in series or parallel. Set a component range and review the closest nominal pairs. - Ohm's law: choose two known quantities from voltage, current, resistance and power to calculate the remaining values. - Voltage divider: find the unloaded output voltage or solve for the lower resistor needed for a target output. See divider current and resistor power. PLAN LED AND TIMING CIRCUITS The LED resistor calculator uses supply voltage, LED forward voltage and target current for a single LED with a series resistor. Review ideal resistance, resistor dissipation, an E24 option, estimated current with that option and a suggested resistor power rating. For a 555 timer, switch between a single monostable pulse and an astable oscillator. Enter resistance and capacitance to calculate pulse duration or frequency, high time, low time and duty cycle. Circuit drawings and an illustrative waveform help connect the inputs with the circuit. The RC calculator shows time constant, first-order filter cutoff frequency and approximate settling at five time constants. Change resistance and capacitance units to explore component choices without converting every value by hand. KEEP USEFUL WORK Recent valid calculations are recorded on the device. Give a result a name, mark a favorite and reopen it to reuse its inputs. Share a text summary containing inputs, results and a circuit or component diagram. Filter the library by recent entries, named saves or favorites. Use the Code, Bands, Network, LED and Timer tabs for core tasks, then open More calculators for the additional tools. Live readouts update as supported inputs change, and light, dark or system appearance lets you choose a comfortable view. Whether you are checking a component from a parts drawer, comparing resistor choices for a breadboard or revisiting a class exercise, keep the calculation and its inputs together. Results use ideal component models; check actual component ratings, tolerances and datasheets for your circuit.