calc.engineer

Calculates the minimum PCB trace width for a given current using the IPC-2221 standard formula. The IPC-2221 empirical equation relates current capacity to cross-sectional area and temperature rise: I = k * dT^0.44 * A^0.725, where k=0.048 for external layers and k=0.024 for internal layers. Supports configurable copper weight (oz/ft^2) and temperature rise. Also computes approximate DC resistance per centimeter. Essential for power delivery, high-current motor drivers, and ensuring PCB reliability. Chain from voltage_divider or impedance_match to verify trace sizing for computed currents.

Convert between units across 10 categories: length (m, km, mi, ft, in, yd, nmi), mass (kg, lb, oz, g, ton), volume (l, gal, ml, cup, fl_oz), area (m2, ft2, acre, hectare), speed (mps, kph, mph, knot), pressure (pa, psi, bar, atm, mmhg), energy (j, kwh, btu, cal, wh), data (b, kb, mb, gb, tb), time (s, ms, min, hr, day, year), and temperature (c, f, k). Accepts any value with source and target unit abbreviations. Returns the converted result with the formula used.

Estimates UPS (Uninterruptible Power Supply) backup runtime from battery specifications and connected load. Takes VA rating, watt rating, load in watts, and battery configuration (count, voltage, amp-hours) to compute effective stored energy after efficiency losses and runtime in minutes and hours. Detects overload conditions when load exceeds the UPS watt rating. Calculates power factor from VA/W ratings. Ideal for server rack planning, homelab power budgeting, network closet UPS selection, and graceful shutdown timer configuration.

Calculates output voltage, current draw, and power dissipation for a resistive voltage divider. Given an input voltage Vin and two resistor values R1 (upper) and R2 (lower), computes Vout = Vin * R2 / (R1 + R2), divider current, individual resistor power dissipation, and the division ratio. Essential for biasing circuits, level shifting, ADC input scaling, and feedback networks. Use before trace_width to size traces for divider current, or chain from a power supply output to verify signal levels.

Calculates voltage drop across a conductor run given current, wire length, AWG gauge, system voltage, and conductor material (copper or aluminum). Computes round-trip resistance, voltage drop in volts and percent, voltage at the load end, power dissipated in the wire, and NEC compliance flags (3% max for branch circuits, 5% max for feeders). Use this after wire_gauge to verify a specific gauge meets requirements, or to evaluate an existing installation. Critical for solar panel string wiring, EV charger circuits, low-voltage lighting, and any long DC or AC cable run where resistive losses matter.

Convert between VSWR, return loss, and reflection coefficient — provide any one parameter and get all related impedance-mismatch metrics. Computes VSWR (voltage standing wave ratio), return loss in dB, reflection coefficient (gamma), mismatch loss, and percentage of power reflected vs transmitted. Essential for antenna matching, transmission line analysis, and RF system budgeting. Feeds into link_budget for system-level mismatch accounting.

Converts electrical power in watts to current in amps (and milliamps) for a given voltage, using the DC power formula P = V * I. Also computes the implied load resistance via Ohm's law (R = V / I) assuming a purely resistive load. This is the most common electrical conversion for circuit design, fuse selection, wire sizing, and breaker rating. Use the output amps value to feed into wire_gauge for conductor sizing or voltage_drop for cable loss analysis. Covers DC circuits; for AC with power factor, adjust watts to true power first.

Convert between radio frequency and wavelength. Provide either frequency in MHz or wavelength in metres, and get the full set of equivalent values: frequency in MHz and GHz, wavelength in metres, centimetres, millimetres, and feet. Essential for antenna dimensioning, waveguide selection, and quick band identification. The fundamental relationship is lambda = c / f where c is the speed of light (299 792 458 m/s).

Determine minimum wire gauge using NEC Table 310.16 ampacity ratings with full derating. Looks up base ampacity for copper or aluminum conductors at 60°C, 75°C, or 90°C insulation rating, then applies NEC 310.15(C)(1) ambient temperature correction and NEC 310.15(C)(2) conductor count adjustment. Automatically applies the 125% continuous load factor per NEC 210.20(A) when flagged. Returns the minimum AWG that meets the derated requirement, plus a comparison table of all gauges. Different from wire_gauge which focuses on voltage drop — use both together for complete wire sizing. Essential for residential panels, commercial feeders, solar arrays, and EV charging installations.

Determines the minimum AWG (American Wire Gauge) conductor size for a given current, voltage, one-way cable distance, and maximum allowable voltage drop percentage. Supports copper and aluminum conductors. Computes round-trip resistance, actual voltage drop in volts and percent, and wire cross-sectional area. Essential for DC solar runs, battery bank wiring, EV charging circuits, and low-voltage landscape lighting. NEC recommends 3% max drop for branch circuits and 5% total including feeder. Outputs the smallest AWG that satisfies the drop constraint.

Calculate the optimal MTU for a WireGuard VPN tunnel interface with a detailed overhead breakdown. Accounts for WireGuard header (32 bytes), outer IP header (20 bytes IPv4 or 40 bytes IPv6), UDP header (8 bytes), and optional PPPoE encapsulation (8 bytes). Prevents fragmentation and PMTUD black holes by computing the maximum inner packet size that fits within the physical link MTU. Essential for WireGuard setup on residential ISP connections (PPPoE), IPv6 tunnels, and any VPN where incorrect MTU causes slow or stalled connections.

Calculate usable ZFS pool capacity for any RAID level including stripe, mirror, raidz1, raidz2, and raidz3. Computes raw capacity, parity overhead, data disk count, usable terabytes after ZFS metadata overhead (checksums, block pointers, uberblocks), and storage efficiency percentage. Essential for planning NAS builds, TrueNAS/ZFS server storage, and estimating how much usable space a given disk configuration will provide. Supports variable disk sizes and configurable metadata overhead.

Calculate recommended RAM and ARC sizing for a ZFS storage pool based on workload type, pool size, deduplication status, and L2ARC cache size. Computes minimum and recommended RAM in gigabytes, ARC target size, and dedup table overhead. Accounts for workload-specific IO patterns: NAS (sequential, 1GB/TB), database (random, 2GB/TB), virtualization (mixed, 1.5GB/TB). Deduplication adds approximately 5GB per TB for the DDT. L2ARC index requires 1GB RAM per 10GB of L2ARC. Essential for TrueNAS, FreeNAS, and custom ZFS server builds.