🧮Calculators
Calculators cover finance, health, math, physics, engineering and everyday life: interest and loans, net salary, BMI, rule of three, conversions and more. Results are informational and educational — for important decisions, confirm with a professional and official sources.
2904 tools
Capacitors in Parallel Calculator
Adds two capacitances in farads to get the equivalent value, Cp = C1 + C2. For example 1 µF plus 4.7 µF gives 5.7 µF, because parallel plates add.
Two Capacitors in Series: Equivalent Capacitance
Enter C1 and C2 in farads for the equivalent value from (C1 x C2)/(C1 + C2), which always lands below the smaller of the two.
Inverting Op-Amp Gain
Enter feedback resistor Rf and input resistor Rin in ohms to get the closed-loop voltage gain Av = −Rf / Rin, negative because the output inverts phase.
Non-Inverting Op-Amp Gain Calculator
Enter the feedback resistor Rf and the ground resistor Rin in ohms to get Av = 1 + Rf/Rin, the closed-loop output-to-input ratio, never below 1.
LED Current-Limiting Resistor
Enter supply voltage, LED forward voltage and target current to get the series resistor in ohms, R = (Vsupply - Vf) / I, then round up to a standard value.
Ohm Law Calculator (V/I/R/P)
Calculate Ohm law by entering any two of voltage (V), current (I), resistance (R) and power (P) — the tool finds the remaining values instantly.
Transformer Turns Ratio Calculator
Finds the secondary voltage of an ideal transformer from V1, N1 and N2 using V1/V2 = N1/N2, so V2 = V1 × N2 / N1: 220 V with 1000:50 turns gives 11 V.
3D Filament Length to Weight
Converts a length of filament in meters into grams from the strand diameter and material density: PLA 1.24, ABS 1.04, PETG 1.27 and TPU 1.21 g/cm3.
Filament Weight to Length Converter
Turns filament weight in grams into length in metres from the strand diameter and the density of the material, with presets for PLA, ABS, PETG and TPU.
3D Print Max Speed from Volumetric Flow
Layer height, line width and the hotend flow limit in mm3/s give the speed ceiling: flow / (height x width). At 15 mm3/s and 0.2 x 0.4 mm, 187.5 mm/s.
Infill Percentage to Print Weight
Estimates the weight in grams of a 3D print from model volume in cm³, infill percentage and filament choice, using PLA, ABS, PETG or TPU density.
3D Print Time Estimator from Volume and Flow
Enter extruded volume in cm³ and effective flow in mm³/s to get hours on the machine: 50 cm³ at 8 mm³/s is 1.74 h, before travel, retraction and supports.
RT60 Sabine
Enter room volume in cubic metres and total absorption in sabins to get reverberation time in seconds from Sabine's equation, RT60 = 0.161 · V / A.
Axial Room Mode Frequency Calculator
Gives the standing wave between two parallel walls, f = n · 343 / (2L) with sound at 343 m/s: a 5 m room resonates at 34.3 Hz on mode 1.
Nyquist Frequency Calculator (Sample Rate / 2)
Enter a sample rate in Hz to get the highest signal frequency it can carry without aliasing, f_max = fs / 2: 44100 Hz yields 22050 Hz.
Bit Depth to Dynamic Range
Enter the bit depth N of a PCM audio file and get the theoretical dynamic range in decibels from DR = 6.02·N + 1.76, the quantization noise ceiling.
Audio Buffer Latency (samples to ms)
Enter buffer size in samples and sample rate in Hz for the one-way delay in milliseconds: samples / rate x 1000, so 256 at 48 kHz gives 5.33 ms.
Paint Calculator (Gallons)
Calculate how many gallons of paint you need for a wall or room, from the area and the coverage per gallon. Avoid buying too much or too little.
Wallpaper Rolls Calculator
Multiplies room perimeter by wall height and divides by the coverage of one roll, rounding up: 12 m by 2.6 m at 5.3 m² per roll needs 6.
Tile Calculator (Rectangular)
Calculate how many tiles to buy for a rectangular area, including the allowance for cuts and waste. Enter the room and tile dimensions.
Diagonal Tile Layout Quantity Calculator
Room width and length in meters plus the square tile side in cm return how many pieces a 45-degree layout needs, with 15% cut waste added on top.
Lumber Linear Feet Calculator
Enter a length in meters and how many pieces to get the total run in feet: m × 3.2808 × pieces, since 1 foot is 0.3048 m. Cross section is ignored.
Board Foot Calculator for Lumber
Converts thickness, width and length in inches plus the piece count into board feet: BF = T × W × L × pieces / 144, so a 2 by 6 by 96 in board is 8 BF.
Concrete Volume Calculator (cubic meters)
Multiplies slab width, length and thickness in meters and returns the cubic meters of ready-mix needed, rounded to 3 decimals; no waste margin added.
Brick Quantity Calculator for Walls
Wall area in m² times bricks per m², plus a waste percentage and rounded up: 20 m² at 25 bricks per m² with 7 percent waste needs 535 units.
Mortar Bags Calculator
Work out how many bags of mortar you need to lay floor or wall tiles from the area and the usage per m². Avoid running short or over-buying on site.
Drywall Sheet Calculator
Calculate how many drywall sheets to buy for walls or ceilings from the area, including the allowance for waste and cuts. Plan your plasterboard project.
Baseboard Calculator
Calculate how many linear meters of baseboard to buy for a room, subtracting the door openings. Plan the right amount for your renovation.
Crown Molding Length Calculator
Enter the ceiling perimeter in meters and a waste percentage for cuts and corners to get the linear meters to buy: total = perimeter × (1 + loss/100).
Tile Grout Quantity Calculator (kg)
Area in m2 plus square tile side, joint width and joint depth estimate how much grout the job takes, at a fixed density of 1.6 g per cm3.
Ceiling Fan Size by Room Area
Enter room area in m² and get the blade span to look for: up to 7 m² 92 cm (36 in), up to 14 m² 122 cm (48 in), up to 22 m² 132 cm (52 in), above that 142 cm.
Air Conditioner BTU Calculator by Room Area
Sizes cooling at 600 BTU/h per square meter plus 600 per extra person and per appliance: 15 m² with 2 people and 2 devices asks for 10,800.
Heater Power kW by Room Area
Multiplies the floor m² by a climate factor of 0.08, 0.1, 0.13 or 0.15 kW/m² to size electric heating: a 20 m² room at 0.1 comes to 2 kW of output.
Attic R-Value by IECC Climate Zone
Choose a zone from 1 (tropical) to 7 (cold) and get the minimum ceiling insulation the US energy code recommends, ranging from R-30 up to R-60.
Lumens per Square Meter Lighting Calculator
Multiply room area by the target lux of the room type (living room 200, kitchen 300, bathroom 500, office 500, bedroom 150) to size total light.
Standard Door Sizes in Brazil (NBR 15930)
Pick the room and read the leaf width used in Brazilian homes: 62 cm bathroom and laundry, 72 bedroom, 82 living room, 92 entrance, all 210 cm tall.
Soil pH Correction: Lime or Sulfur
Enter current pH, target pH and plot area in m² to get grams of dolomitic limestone to raise it, or of elemental sulfur to lower it, per pH point.
NPK Fertilizer Ratio Calculator
Turns an NPK label such as 10-10-10 into grams of each nutrient for the amount of fertilizer you weigh out: 100 g of 10-10-10 carries 10 g of each.
Weekly Plant Watering Calculator
Multiplies a base of 0.2 to 2.5 liters by plant type, from succulent to vegetable bed, by a climate factor of 0.7 to 1.4 and by how many pots you keep.
Compost C:N Ratio Calculator
Divides grams of carbon by grams of nitrogen in a compost mix and says whether the pile needs more browns or more greens to sit near the ideal 25-30:1.
Square Foot Gardening Plant Capacity
Pick one of four crops and how many 30 cm squares you have to get the plant total: tomato 1 per square, lettuce 4, beet 9 and carrot 16.
Seed Planting Depth Calculator
Applies the rule of thumb of 2 to 3 times the seed diameter: enter 5 mm and the sowing range comes out as 10 to 15 mm deep in the soil.
Vegetable Seedling Spacing Lookup
Pick lettuce, tomato, carrot, onion, arugula or basil and read the recommended row × plant spacing in cm, from carrot 25×8 cm to tomato 100×60 cm.
Mulch Calculator: Cubic Feet of Coverage
Enter bed area in square meters and layer depth in centimeters to get the volume in cubic feet: 10 m2 at 7 cm deep needs 24.72 cu ft.
Frost Risk Window by Brazilian Region
Pick one of Brazil's five regions for the climatological frost window: April to September in the South, May to August in Southeast highlands.
Days to Harvest by Crop
Pick one of eight garden crops and see the usual span from sowing to picking: arugula 30 to 40, lettuce 45 to 60, tomato and potato 90 to 120.
Hydroponic Pump Cycle: NFT, DWC and Ebb and Flow
Pick one of three systems for the recommended timer setting: NFT runs nonstop at 1 to 2 L/min, DWC 15 minutes on and 15 off, Ebb and Flow 15 on 45 off.
Hydroponic Nutrient EC by Growth Stage
Pick the crop stage and get the target electrical conductivity in mS/cm: seedling 0.6-0.9, vegetative 1.2-1.7, flowering 1.6-2.0, fruiting 1.8-2.4.
Daily Cat Litter Usage Calculator
Estimates the grams of litter scooped out per day from how many cats share the box: roughly 150 g for one cat, 270 g for two and 360 g for three.
Aquarium Stocking: 1 Inch per Gallon
Tank volume in liters and average adult fish length in cm return how many fish the old hobby rule allows, at 3.785 L per gallon and 2.54 cm per inch.
Aquarium Cycling Time Estimator
Say whether you are dosing a bottled bacteria starter and get how long the nitrogen cycle should take: 7 to 14 days with it, 4 to 8 weeks without it.
Terrarium Humidity by Reptile Species
Pick from 5 species for the target relative humidity: leopard gecko and bearded dragon 30-40%, crested gecko 60-80%, corn snake 40-50%.
Minimum Bird Cage Size by Species
Pick canary, budgie, cockatiel, lovebird or parrot and read the smallest enclosure in cm, width x depth x height, from 45x30x40 up to 120x90x150.
Daily Dog Walking Time by Size and Energy
Pick a size and an energy level to get suggested minutes per day: a base of 20, 40, 60 or 75 min scaled by 0.7, 1 or 1.5 for low, medium or high.
Minimum Hamster Wheel Diameter by Species
Looks up the smallest safe running wheel for dwarf, Chinese and Syrian hamsters, 21, 25 and 28 cm, so the spine stays flat instead of arching.
Weighted Grade Average Calculator
Paste grades and their weights as two comma-separated lists to get the sum of grade times weight divided by total weight, rounded to 2 decimals.
Weighted Report Card Average, 4 Terms
Enter four term grades from a Brazilian school report card and a weight for each to get Σ(grade × weight) / Σweight, rounded to two decimals.
Weighted GPA Calculator
Calculate your weighted grade point average by weighting each course grade by its credit hours. Track your academic performance throughout the degree.
ENEM Target Average: Score Still Needed
Enter the goal, the scores already earned and how many tests are left to get the mean still needed on ENEM, Brazil's university entrance exam.
CEFR Level by Study Hours
Enter the hours you have logged and see the band it puts you in: 70 hours for A1, 180 A2, 350 B1, 550 B2, 800 C1 and 1200 for C2 on the CEFR scale.