gizmo421

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Small tools that just work.

Free calculators, generators, and utilities built to do one thing well. No accounts, no clutter, and nothing you type ever leaves your device.

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Age Calculator

Exact age in years, months, and days from a birthdate, plus totals and a next-birthday countdown.

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Aspect Ratio Calculator

Scale resolutions without distortion — 16:9, 4:3, 9:16 — and solve the missing dimension.

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Bandwidth Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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Basic Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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BMI Calculator

Body mass index in US or metric units, with weight category and a healthy weight range.

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Calorie Calculator

Daily calorie targets: BMR, maintenance (TDEE), and weight loss or gain goals, US or metric.

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Compound Interest Calculator

Watch savings grow: final balance, total invested, and interest earned — plus a year-by-year table.

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Concrete Calculator

Figure out how many cubic yards of concrete a slab, footing, or column needs.

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Date Calculator

Days between two dates, or add and subtract days, weeks, months, and years from any date.

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Discount & Sales Tax Calculator

The real checkout price: sale price after a discount, sales tax, and the final total.

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Electricity Cost Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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Final Grade Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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Fuel Cost Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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GPA Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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Loan Payoff Calculator

Months to pay off a loan, total interest, and how much an extra monthly payment saves.

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Mortgage Calculator

Estimate monthly mortgage payments with taxes, PMI, and full amortization schedule.

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Percentage Calculator

What is X% of Y, percent change, and "is what percent" — solved live as you type.

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Scientific Calculator

A scientific calculator with trig, logs, powers, factorials, and a live result preview.

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Sleep Calculator

Bedtimes and wake times built around 90-minute sleep cycles, so you wake between cycles instead of mid-dream.

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Speed, Distance & Time Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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Time Card Calculator

A free browser-based tool. Nothing you enter ever leaves your device.

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Time Duration Calculator

Find the exact duration between two times, or add and subtract hours and days from any date.

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Tip Calculator

Tip amount, total, and per-person split for any bill — with quick 10-20% preset buttons.

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Unit Converter

Convert length, weight, temperature, volume, area, and speed — metric and US units, live.

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// from the blog

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