calc.engineer
89 engineering tools — SPICE simulator, PCB autorouter & calculators. Free, instant, no login.
RF & Antennas 13
FSPL
Calculate free-space path loss (FSPL) in decibels using the ITU-R P.525 standard formula.
Link Budget
Compute a full RF link budget from transmitter power, frequency, distance, and antenna gains.
Dipole
Calculate physical dimensions of a dipole antenna for a given frequency.
Microstrip
Calculate PCB microstrip trace width for a target characteristic impedance using the Hammerstad-Jensen closed-form eq…
dBm Convert
Convert a power level in dBm to milliwatts, watts, dBW, and RMS voltage across a given impedance.
Noise Figure Cascade
Calculate the cascaded noise figure of a multi-stage receiver chain using the Friis formula.
VSWR
Convert between VSWR, return loss, and reflection coefficient — provide any one parameter and get all related impedan…
Attenuator Pi
Design a Pi-topology resistive attenuator pad.
Attenuator Tee
Design a Tee-topology resistive attenuator pad.
Fresnel Zone
Calculate the Fresnel zone radius at the midpoint of a radio link.
Wavelength Freq
Convert between radio frequency and wavelength.
SPICE Template
Generate a complete SPICE netlist from a parameterized template.
SPICE Simulate
Run a SPICE circuit simulation directly in the worker.
LoRa & Meshtastic 10
LoRa Airtime
Calculates LoRa packet time-on-air using the Semtech AN1200.13 formula.
SNR Margin
Computes LoRa link SNR margin by comparing received power against the noise floor and the spreading-factor-dependent …
Channel Utilization
Estimates Meshtastic or LoRa mesh channel utilization percentage based on node count, message rate, and per-packet ai…
LoRa Range Estimate
Estimates LoRa maximum communication range by computing the free-space path loss (FSPL) link budget and applying terr…
LoRa Sensitivity
Calculates LoRa receiver sensitivity from spreading factor, bandwidth, and noise figure using the Semtech SX1276 data…
Duty Cycle Budget
Calculates LoRa duty cycle budget for EU868, US915, AS923, and AU915 regulatory regions.
Meshtastic Range
Estimates Meshtastic node communication range using real hardware profiles and firmware channel presets.
EIRP Compliance
Checks EIRP (Effective Isotropic Radiated Power) compliance against regional regulatory limits for LoRa and Meshtasti…
Meshtastic Power
Calculates Meshtastic node power consumption and battery runtime using device-specific power profiles and firmware ro…
LoRa Param Optimizer
Recommends optimal LoRa spreading factor, bandwidth, and TX power based on target range, terrain, and optimization pr…
Homelab & Networking 13
ZFS Capacity
Calculate usable ZFS pool capacity for any RAID level including stripe, mirror, raidz1, raidz2, and raidz3.
ZFS Ram
Calculate recommended RAM and ARC sizing for a ZFS storage pool based on workload type, pool size, deduplication stat…
TCP Throughput
Calculate maximum TCP throughput using the Bandwidth-Delay Product (BDP) formula.
Wireguard MTU
Calculate the optimal MTU for a WireGuard VPN tunnel interface with a detailed overhead breakdown.
Subnet Calculator
Calculate IPv4 subnet details from CIDR notation.
RAID IOPS
Estimate RAID array IOPS performance and latency for ZFS and traditional RAID configurations.
Power Cost
Calculate total power consumption, electricity cost, and circuit requirements for a homelab.
Cooling BTU
Estimate the cooling load (BTU/hr) for a homelab or server closet based on equipment wattage, room dimensions, insula…
Rack Capacity
Quick rack space and weight sizing calculator for homelab and small data center racks.
Network Bandwidth
Plan and validate network link capacity for homelab workloads.
Thermal Enclosure
Estimate steady-state thermal behaviour of a rectangular enclosure (server rack, electronics housing, equipment cabin…
Heatsink CFD
Analyze a forced-convection fin-array heatsink using established channel-flow correlations (developing laminar Nussel…
PCB Thermal
Estimate PCB component temperatures by solving a thermal resistance network (thermal↔electrical analogy) with the bui…
Solar & Power 15
Battery Life
Calculates battery runtime and energy capacity given cell capacity in mAh, nominal voltage, and average current draw.
Wire Gauge
Determines the minimum AWG (American Wire Gauge) conductor size for a given current, voltage, one-way cable distance,…
Solar Sizing
Sizes an off-grid solar power system by calculating the number of panels and battery bank capacity required for a giv…
UPS Runtime
Estimates UPS (Uninterruptible Power Supply) backup runtime from battery specifications and connected load.
mAh To Wh
Converts battery capacity from milliamp-hours (mAh) to watt-hours (Wh), kilowatt-hours (kWh), and joules (J) given th…
Watts To Amps
Converts electrical power in watts to current in amps (and milliamps) for a given voltage, using the DC power formula…
Voltage Drop
Calculates voltage drop across a conductor run given current, wire length, AWG gauge, system voltage, and conductor m…
Battery Charge Time
Estimates battery charge time given capacity in mAh, charge current in mA, charger efficiency, and initial state of c…
Solar Load Audit
Calculates total daily energy consumption from an appliance list — the critical first step before sizing solar panels…
Solar ROI
Calculates solar system return on investment, payback period, and levelized cost of energy (LCOE).
Battery Autonomy
Calculates how many days a battery bank can sustain loads without solar input — critical for off-grid and backup powe…
String Sizing
Calculates optimal solar panel string and MPPT configuration based on panel electrical specs, inverter/charge-control…
Generator Offset
Compares total cost of ownership between a fuel generator and a solar+battery system over a configurable time horizon.
Wire Ampacity
Determine minimum wire gauge using NEC Table 310.16 ampacity ratings with full derating.
Inverter Sizing
Size a DC-to-AC inverter for off-grid solar, battery backup, or mobile power systems.
PCB & Electronics 14
PCB Layout
Turn a SPICE netlist into a fab-ready 2-layer PCB: assigns real footprints (0805, TO-92, DO-35, DIP-8, headers, LED, …
Voltage Divider
Calculates output voltage, current draw, and power dissipation for a resistive voltage divider.
RC Filter
Computes the cutoff frequency, time constant, impedance, and phase shift of a first-order RC filter.
LC Resonance
Calculates the resonant frequency of an LC circuit, along with optional Q factor and bandwidth when series resistance…
Impedance Match
Designs an L-network impedance matching circuit between two real impedances at a given frequency.
Trace Width
Calculates the minimum PCB trace width for a given current using the IPC-2221 standard formula.
Ohms Law
Solves Ohm's Law and the power equation given any two of four electrical quantities: voltage (V), current (I), resist…
Resistor Color Code
Decodes 4-band or 5-band resistor color codes into resistance value, tolerance, and min/max range.
LED Resistor
Calculates the current-limiting resistor for driving one or more LEDs in series from a DC supply.
Timer 555
Calculates timing parameters for the ubiquitous NE555 / LM555 timer IC in astable (free-running oscillator) and monos…
Op Amp Gain
Calculate voltage gain and output for operational amplifier circuits in inverting, non-inverting, and differential co…
Capacitor Charge
Calculates RC capacitor charge timing, energy storage, and transient voltages.
PCB Via Current
Calculate PCB via current-carrying capacity using the IPC-2221 standard.
Power Supply Decoupling
Select bypass and bulk decoupling capacitors for IC power supply pins.
General & Math 24
Log Calc
Compute logarithms of a positive number in any base.
Sig Figs
Count significant figures in a number and optionally round to N significant figures.
Scientific Notation
Convert any number to scientific notation and engineering notation.
Percentage Calc
Calculate what percentage one number is of another.
Percentage Increase
Calculate the percentage change between an old value and a new value.
Exponent Calc
Compute the result of raising a base to an exponent (base^exponent).
Square Root
Compute the square root of a non-negative number.
Circumference
Calculate the circumference and area of a circle given either a radius or diameter.
Slope Calc
Calculate the slope, y-intercept, line equation, angle, and distance between two points in a 2D Cartesian plane.
Pythagorean Theorem
Solve for any side of a right triangle using the Pythagorean theorem (a² + b² = c²).
P Value
Calculate the p-value for a z-score or t-statistic.
Confidence Interval
Calculate the confidence interval for a sample mean.
Sales Tax
Calculates total cost including sales tax for a purchase.
Salary To Hourly
Converts compensation between annual salary, monthly pay, weekly pay, and hourly wage.
Loan Amortization
Computes a full loan amortization schedule given principal, annual interest rate, and term in months.
Compound Interest
Calculates compound interest growth over time using the formula A = P(1 + r/n)^(nt).
Test Grade
Calculates a test or exam grade from the number of correct answers and total questions.
Square Footage
Calculates area and perimeter for common shapes — rectangle, circle, or triangle — in both imperial and metric units.
Unit Convert
Convert between units across 10 categories: length (m, km, mi, ft, in, yd, nmi), mass (kg, lb, oz, g, ton), volume (l…
Hex Converter
Convert numbers between hexadecimal, binary, decimal, and octal bases.
Timestamp Converter
Convert between Unix timestamps and human-readable date/time formats.
BMI Calculator
Calculate Body Mass Index (BMI) from weight and height using the WHO standard formula.
Tip Calculator
Calculate tip and split a restaurant bill among multiple people.
Date Difference
Calculate the difference between two dates in days, weeks, months, years, and business days.