Embedded Calculators & Part Finder
Size a value with 64 free calculators, then find the real component that fits — in stock, at the best price. For MCU, power, RF & firmware. No account.
★ Popular
💡LED Resistor
⚡Ohm's Law
🚌CAN Bit Timing
🔻Voltage Divider
🔠Glyph Mapper
📦Struct Padding
PWM / Timer
Frequency, period, duty cycle
UART Baud Rate
Error rate, PASS/FAIL check
ADC Resolution
LSB voltage, SNR, dynamic range
Watchdog Timer
STM32 IWDG & WWDG timeouts
I2C Timing
Bus timing & pull-up values
CAN Bus Bit Timing
STM32 bxCAN/FDCAN & MCP2515
SPI Timing
Bit period, frame, throughput
RS-485 Bus
Cable length, termination, bias
LIN Bus Timing
Bit, break, frame time
Modbus RTU Timing
Char & inter-frame gaps
Ring Buffer / DMA
Buffer sizing
Register Map → C
Bitfield struct & macros
CRC → C Code
Lookup table & function
Stepper Motor
Steps/rev, microstep, pulse rate
BLDC / PMSM Speed
Motor electrical freq, pole pairs
Rotary Encoder
Motor encoder counts/rev
Motor Torque ↔ Power
N·m, RPM, Watts, hp
MOSFET Power Loss
Conduction & switching loss
Transformer Turns
Ratio, Ns, current ratio
LDO Dropout / Power
Heat dissipation & efficiency
I2S Audio Clock
BCLK, LRCLK, bit period
USB Data Lines
Bit time, 90Ω, termination
Ethernet Cable
Bit time, delay, 100m limit
Bit Field Visualizer
32-bit register breakdown
Q-Format Converter
Float ↔ fixed-point
Number Base Converter
Dec, Hex, Bin, Oct converter
IEEE 754 Visualizer
32-bit Float & 64-bit Double
Endian Swap
Big/Little/Mid-Endian byte swap
Struct Alignment
C struct padding & visualizer
Memory & Transmission
Bytes, baud rate & sample times
Glyph Mapper
7-Segment & Character LCD custom font generator
Crystal Load Cap
Oscillator load capacitor sizing
Ohm's Law
V, I, R, P — any 2 → all 4
Voltage Divider
Vout, loaded divider, Thevenin
LED Resistor
Series/parallel configs & E24
Resistor Code
Color bands & SMD decoder
Op-Amp Gain
Amp configurations & Schmitt
Instrumentation Amp
3-op-amp in-amp gain & Vout
Op-Amp Resistor
Inverting/Non-inv → R2,R3,R4
BJT Bias CE
Q-point & stability factor
NE555 Timer
Astable / monostable
Capacitor Charge
RC time constant, τ milestones
Buck / Boost
Switching regulator design
AWG Wire Gauge
Wire gauge & voltage drop
Series / Parallel
R · C · L equivalent value
LM317 Regulator
Adjustable Vout & R2 solver
Current Divider
Branch currents in parallel R
LC Resonance
LCR resonant freq, Q-factor
RC Filter
Cutoff frequency, gain & phase
dB Converter
dB, dBm & mW bidirectional
CRC Calculator
CRC-8/16/32, 7 polynomials
Checksum / CRC
XOR, Sum8/16, LRC, CRC
PCB Trace Calc
IPC impedance & trace width
Active Filter
Sallen-Key 2nd-order LPF/HPF
RF Trans. Line
Microstrip impedance (IPC-2141)
VSWR / Return Loss
Γ, return & mismatch loss
RF Link Budget
FSPL, Rx power, margin
Wavelength / Antenna
λ, λ/2 dipole, λ/4 whip
Attenuator Pad
T / Pi resistor values (dB)
Coil Inductance
Air-core solenoid (Wheeler)
Battery Life
Estimated system run-time
Temperature
Units & RTD sensor temps
Wheatstone Bridge
Bridge Vout & balance
Junction Temp
Thermal Tj & max power
LM317 Voltage Regulator Calculator
Calculate the output voltage of an LM317 adjustable regulator, and the resistor needed for a target voltage.
Input
ℹ R1 is typically 240 Ω. Iadj ≈ 50 µA (often negligible).
Results
Output Voltage (Vout)—
Required R2 for Target Vout—
💡 Usage & Formula
LM317 sets its output by holding Vref (≈1.25 V) across R1, so the divider R1/R2 programs Vout.
- Output:
Vout = Vref × (1 + R2/R1) + Iadj × R2 - Required R2:
R2 = (Vout − Vref) / (Vref/R1 + Iadj)
Usage: Keep R1 ≈ 240 Ω, set R2 for the voltage you need, or type a Target Vout to get the exact R2. Minimum Vout = Vref (1.25 V).
When you need it: Setting an adjustable linear regulator's output with two resistors, or wiring it as a simple constant-current source for an LED string or battery charger.
Worked example: Vout = 1.25 × (1 + R2/R1); with R1 = 240 Ω, R2 = 720 Ω → 1.25 × (1 + 3) = 5.0 V. As a current source, I = 1.25 / R.
Tips & gotchas:
- Keep the standard
R1 ≈ 240 Ωso the regulator's minimum load current is always met. - Dissipation is
(Vin − Vout) × I— a large drop at high current needs a real heatsink. - It needs roughly 2.5–3 V of headroom (dropout); an LDO is better when Vin is close to Vout.
- Add the datasheet protection diodes when using large output or adjust-pin capacitors.
📖 References:
LM317 (Wikipedia)