Featured contributor MSc Applied Statistics; 7 years in analytics and data tooling.

Daniel Oh

Senior Contributor, Math & Statistics

0 calculators 0 articles Member since Jun 2026

About

Daniel writes and reviews the math and statistics calculators. His explainers lean on worked examples, clean formulas, and obvious edge cases so readers can copy the logic straight into a spreadsheet.

He previously worked as a data scientist at a consumer-tech startup before moving into full-time writing and tooling.

Areas of expertise

Statistics Probability Percentages Data analysis

Education & credentials

BSc Mathematics — University of Toronto
MSc Applied Statistics — ETH Zürich

Math

Sum of Squares from 1 to n Calculator

Compute the closed-form sum of the first n positive squares: 1² + 2² + ⋯ + n² = n(n+1)(2n+1)/6. The classical Faulhaber...

basic

10,976 4.7 1 min

Ecology / Energy

Electricity Bill Calculator

Estimate the monthly electricity cost of an appliance from its wattage, daily use, and your tariff.

basic

5,103 4.3 1 min

Chemistry / Solutions

Combined Gas Law Calculator

Find the missing pressure, volume, or temperature using the combined gas law for a fixed amount of gas.

basic

5,359 4.2 1 min

Physics

Decibel Level from Intensity Ratio Calculator

Converts an intensity ratio or pressure ratio to decibels: dB_power = 10·log₁₀(I₁/I₀); dB_amplitude = 20·log₁₀(A₁/A₀). I...

basic

3,937 4.9 1 min

Math

Complex Number — Rectangular to Polar Calculator

Convert a complex number from rectangular form a + b·i to polar form r∠θ, with r = √(a² + b²) and θ = atan2(b, a). Repor...

basic

5,364 4.4 1 min

Physics / Electricity

Capacitance Calculator

Compute the capacitance of a parallel-plate capacitor from plate area, plate separation, and the dielectric constant.

basic

12,524 4.1 1 min

Math / Percentage

Percentage Calculator

Solve every common percentage question — "what is X% of Y", "X is what percent of Y", and percentage change.

Featured Trending basic

23,355 4.6 1 min

Chemistry / Solutions

pOH Calculator

Compute pOH from hydroxide ion concentration and the matching pH at 25 °C.

basic

18,221 4.2 1 min

Math

Two-Proportion Z-Test Calculator

Test whether two independent sample proportions differ significantly. Pooled estimate p̄ = (x₁ + x₂)/(n₁ + n₂); z = (p̂₁...

basic

1,822 4.2 1 min

Everyday Life / Shopping

Gift Cost Split Calculator

Compute how much each person owes when splitting a group gift, with optional shipping and an organizer's share.

basic

16,211 4.1 1 min

Everyday Life / Time & Date

Day of the Week Calculator

Find the day of the week for any past or future date, plus the day-of-year, ISO week number, and how far the date is fro...

basic

2,237 4.8 1 min

Finance

Inventory Turnover & Days on Hand Calculator

Calculates inventory turnover ratio and days on hand from cost of goods sold and average inventory to assess operational...

basic

5,589 5.0 1 min

Showing 13 to 24 of 545 results

tutorial Math

Percentages Without the Headache

Every "X% of Y" problem, every "what percent of", every percent-change question — written out the way you'd actually say them.

Daniel Oh

Jan 16, 2026 3 min

explainer Statistics

Standard Deviation in Five Minutes

Standard deviation is "average distance from the average". That one sentence covers 90% of everything you ever need to remember about it.

Daniel Oh

Dec 6, 2025 3 min

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Browse categories

Daniel Oh

Sum of Squares from 1 to n Calculator

Electricity Bill Calculator

Combined Gas Law Calculator

Decibel Level from Intensity Ratio Calculator

Complex Number — Rectangular to Polar Calculator

Capacitance Calculator

Percentage Calculator

pOH Calculator

Two-Proportion Z-Test Calculator

Gift Cost Split Calculator

Day of the Week Calculator

Inventory Turnover & Days on Hand Calculator

Percentages Without the Headache

Standard Deviation in Five Minutes