🧮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
Equivalent Exposure by ISO (Shutter Speed)
Keeps brightness constant when the sensitivity changes: t2 = t1 × (ISO1/ISO2), so 1/125s at ISO 400 becomes about 1/31s at ISO 100.
Circle of Confusion by Sensor Size
Pick a sensor format to get the CoC in mm that depth of field and hyperfocal math need: full frame 0.030, APS-C 0.020, MFT 0.015, 1 inch 0.011.
Camera Field of View (FOV) Calculator
Enter focal length and sensor width in mm to get the horizontal angle of view: 2 x arctan(width / 2f) in degrees. A 50 mm lens on 36 mm gives 39.6.
ND Filter Stop Reduction Calculator
Type the neutral density factor and read the light loss in stops as log2 of that factor: ND8 costs 3 stops, ND64 costs 6 and ND1000 costs about 9.97.
Flash Guide Number to Aperture
Works out the f-number for a flash exposure from the guide number in meters at ISO 100 and the subject distance, using the relation N = GN / d.
Time-Lapse Interval Calculator
Enter final clip length, video frame rate and how long the event lasts to get the seconds to wait between shots and the total number of frames needed.
Video File Size from Bitrate Estimator
Bitrate in Mbps times duration in seconds divided by 8 gives the size in MB: 30 minutes of 1080p H.264 at 8 Mbps lands near 1800 MB, or 1.8 GB.
Knitting Gauge Calculator (Stitch Count)
Turns a swatch measured in stitches per 10 cm plus a target width in cm into the stitches to cast on: width × gauge / 10, rounded to a whole stitch.
Yarn Estimator for Knitting Projects
Multiplies project area in cm² by average yarn use in m/cm² (scarf 0.4, sweater 0.5) to estimate meters to buy: 5000 cm² at 0.4 needs 2000 m.
Sewing Pattern Grading Calculator
Enter a base measurement in cm and how many sizes up or down you are going: each step scales it by 4 percent, so 90 cm two sizes up is 97.2 cm.
Fabric Yardage Calculator for Sewing Projects
Enter pattern area in cm² and bolt width in cm, 140 cm by default, to get linear meters of fabric with a 15% cutting waste margin built in.
Embroidery Stitch Count by Area
Multiplies design area in square centimeters by stitch density (fine 120, medium 80, coarse 40 per sq cm) to estimate the total stitch count.
Knitting Row Count Calculator from Gauge
How many rows a target length needs: centimetres times the swatch gauge in rows per 10 cm, divided by 10 and rounded. 60 cm at 30 rows per 10 cm is 180.
Fabric Dye Calculator: Percent of Fabric Weight
Multiplies the dry weight of the cloth in grams by the depth of shade you want, to get grams of dye: 300 g of fabric at 3 percent needs 9 g.
Bracelet Beads
Calculate number of beads for a bracelet: length (cm) / bead diameter (mm) × 10.
Key Signature Lookup by Major Key
Pick one of the 15 keys from C to C flat and read how many accidentals it carries: G returns 1 sharp, E flat returns 3 flats and C returns none at all.
Note Transposition by Semitones
Pick a note and shift it by N semitones, up or down, across the 12 pitch classes: C plus 5 gives F, C plus 7 gives G, wrapping around past B.
Secondary Dominants of a Major Key
Pick the tonic and get one dominant seventh chord per diatonic degree, labelled V/ii, V/iii, V/IV, V/V and V/vi. In C that runs A7, B7, C7, D7, E7.
Relative and Parallel Minor Keys
Choose a major key and see its relative minor, which keeps the same key signature, and its parallel minor, which keeps the same tonic but changes the signature.
CTR (Click-Through Rate)
Divides clicks by impressions to give the click-through rate as a percentage, then rates it low, average, good or excellent against ad benchmarks.
Simple Conversion Rate Calculator
Divides conversions by visitors and multiplies by 100, then grades it: under 1 percent is low, 1 to 3 average, 3 to 5 good, 5 or more excellent.
CPC (Cost per Click) Calculator
Calculate the CPC (cost per click) of your campaigns by dividing spend by the number of clicks. Track ad efficiency on Google Ads and Meta Ads.
CAC (Customer Acquisition Cost)
Divides total marketing and sales spend by the number of new customers won in the same period, giving the average cost of acquiring one customer.
LTV (Lifetime Value)
Multiplies average ticket by purchases per month and retention in months, so you see how much revenue a single customer brings over the whole relationship.
LTV:CAC Ratio
Divide customer lifetime value by acquisition cost and read the verdict: below 1 you lose money, 3 or more is healthy, above 5 hints at underinvestment.
Amazon Ads ACoS Calculator
Divides ad spend by attributed revenue to return ACoS as a percentage, rated from excellent below 15% to high above 40%. It is the inverse of ROAS.
CAC Payback Period in Months
Divides customer acquisition cost by monthly revenue per customer times gross margin, showing how many months it takes to earn the acquisition spend back.
Monthly Churn Rate
Divides customers lost by the headcount at the start of the month to get churn as a percentage, banded from under 2% (excellent) to above 10% (high).
NPS (Net Promoter Score)
Takes counts of promoters (9-10), passives (7-8) and detractors (0-6) and returns the NPS on the -100 to 100 scale, plus the band it falls in.
A/B Test Significance Calculator (Chi-Square)
Visitors and conversions of variants A and B in a 2x2 table return the statistic; past 3.84 with 1 degree of freedom the gap is significant at p 0.05.
Email Open Rate Calculator
Enter emails sent, bounces and unique opens to get the rate on delivered mail: opens ÷ (sent − bounces) × 100. Above 30% rates as excellent.
Email Bounce Rate Calculator
Bounces divided by messages sent times 100, with a rating: under 1 percent is excellent, past 2 percent your sender reputation starts to suffer.
5-Step Funnel Drop-off Rate
Enter the user count at each of 5 stages for the four step-to-step losses, 1 minus out/in, plus end-to-end conversion from stage 1 to stage 5.
Average Order Value (AOV)
Calculate your average order value (AOV) by dividing total revenue by the number of orders. A key metric for tracking sales in e-commerce.
Repeat Purchase Rate Calculator
Divides returning customers by total customers for the repeat purchase rate as a percentage, banded from low under 10% to excellent at 40% or above.
RFM Customer Segmentation Score
Score recency (1 is the most recent), frequency and monetary value from 1 to 5 to get the total and a label: Champion, Loyal, At Risk or Lost.
TDEE from BMR and Activity Factor
Multiplies basal metabolic rate in kcal by an activity factor between 1.2 (sedentary) and 1.9 (athlete) to give total daily energy expenditure in kcal per day.
Macronutrient Split by Percentage of Calories
Turns a daily calorie target and your protein, carb and fat shares into grams at 4, 4 and 9 kcal/g: 2200 kcal at 30/40/30 gives 165 g of protein.
Calories Burned by Steps
Estimate how many calories you burn walking from your step count and body weight. Track the energy spent on your daily step goals.
BMR vs RMR Difference Calculator
Type the basal rate in kcal to see the resting value and the gap between them: resting metabolism runs about 10 percent higher, 1500 becomes 1650.
Waist-to-Hip Ratio (WHR)
Divides waist by hip circumference in centimeters and reads the result against the cardiovascular risk cut-offs of 0.90 for men and 0.85 for women.
WHtR Waist-to-Height Ratio
Enter waist and height in centimetres for the waist-to-height ratio and its band: under 0.5 healthy, 0.5 to 0.6 raised, 0.6 and up high cardiometabolic risk.
Apgar Score Calculator and Interpretation
Adds the five newborn signs, appearance, pulse, grimace, activity and respiration, scored 0 to 2: 7 to 10 is normal, 4 to 6 moderate, 0 to 3 severe asphyxia.
MELD Score Calculator for Liver Disease
Bilirubin, INR and creatinine give 3.78 ln(bili) + 11.2 ln(INR) + 9.57 ln(creat) + 6.43, the original index ranking liver transplant priority.
CHA2DS2-VASc Stroke Risk Score in Atrial Fibrillation
Add the eight CHA2DS2-VASc items — heart failure, hypertension, age, diabetes, prior stroke, vascular disease, sex — for a total out of 9 and its risk band.
HAS-BLED Bleeding Risk Score
Adds the seven HAS-BLED items, from hypertension and labile INR to age over 65 and drug or alcohol use, and rates bleeding risk under oral anticoagulation.
ASCVD Cardiovascular Risk (Simplified)
Simplified 10-year ASCVD estimate from age, sex, smoking, diabetes, treated hypertension and total cholesterol, returning a percentage and its risk band.
Wells Score for DVT
Score the nine Wells criteria for deep vein thrombosis, including an alternative diagnosis worth −2, for a total with low, moderate or high probability.
qSOFA Score (Sepsis)
Adds the three qSOFA criteria, respiratory rate 22 or above, Glasgow under 15 and systolic pressure 100 or less, and flags 2 or more as high risk.
Macro Calories Calculator
Calculate the calories of a meal from grams of protein, carbs and fat (4/4/9 kcal per gram). Ideal for dieting and counting macros.
Net Carbs (Keto)
Subtracts fiber and half the sugar alcohols from total carbohydrate, all in grams, leaving the net carbs that count against a ketogenic daily limit.
Daily Water Intake by Activity Level
Estimates daily fluid needs in liters from body weight and training time: 35 mL per kg of body weight plus 500 mL for each hour of exercise.
Glycemic Load (GL) Calculator
Enter the glycemic index and the available carbs per serving in grams: GL = GI x carbs / 100. Up to 10 is low, 11 to 19 medium, 20 or more high.
Recommended Daily Fiber Intake
Turns your daily calorie intake into a fiber target in grams using the IOM reference of 14 g per 1000 kcal, so 2000 kcal a day means 28 g.
Daily Sodium Intake Limit Checker
Rates a figure in mg against the 1500 mg ideal and the 2300 mg cap, and converts it to table salt at 2.5 times the mass: 2300 mg of it sits in 5.8 g of salt.
WHO Free Sugar Daily Limit Calculator
Daily calories turn into grams of free sugar at both WHO caps: 10 percent of kcal over 4, and the stricter 5 percent. 2000 kcal allows 50 g or 25 g.
Saturated Fat Daily Limit
Turns a daily calorie target into grams of saturated fat at the WHO ceiling of 10% of energy and at the stricter 7% the AHA advises for heart risk.
Omega-6 to Omega-3 Ratio
Enter the grams of each fat family eaten per day for the ratio and a verdict: up to 4:1 is healthy, past 4:1 is over the ideal, past 10:1 inflammatory.
Alcohol Calorie Calculator by ABV
Enter volume in ml and ABV percent to get the calories from ethanol alone: ml x ABV/100 x 0.789 x 7. A 350 ml can at 5 percent is about 97 kcal.
Caffeine Half-Life Calculator
Find out how much caffeine is still in your body after a few hours, using the roughly 5-hour half-life. Enter the dose and the time elapsed.