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Viralrang

Guides & how-tos

Practical answers with the math shown โ€” every guide pairs with a free calculator. Written by Mohamed Zakrya.

How Are Loan Payments Calculated? Amortization, Explained

One level payment, front-loaded interest โ€” the formula worked by hand, the two levers you control, and why the smaller payment is often the costlier loan.

July 23, 2026 ยท 13 min read

How Many Solar Panels Do I Need? Sizing From Your Real Usage

Daily usage divided by what one kilowatt makes in a day, why sun hours dominate the count, and the wattage trade that saves a tight roof.

July 23, 2026 ยท 13 min read

How Much Does It Cost to Charge an EV? Home vs Public, Per Mile

The three-line formula, the losses you pay for but never keep, and why home charging beats public by two to four times.

July 23, 2026 ยท 13 min read

How Much Protein Do I Need a Day? Grams by Goal and Body Weight

Your weight in kilograms times a goal factor. The factor is the whole story โ€” and the range matters more than the number.

July 23, 2026 ยท 13 min read

How Much Should You Tip? Rates by Situation, With the Math

The customary rates by setting, the three-line formula, and the split order that keeps the tip at the rate you chose.

July 23, 2026 ยท 12 min read

How to Calculate Take-Home Pay: From Gross to What You Keep

One combined deduction rate, your pay schedule, and a two-minute pay stub calibration โ€” gross to net in two lines of math.

July 23, 2026 ยท 13 min read

What Is TDEE? Total Daily Energy Expenditure, With Real Numbers

The resting floor, the activity multiplier that scales it, and how to read the maintenance number that comes out.

July 23, 2026 ยท 13 min read

How Does Compound Interest Work? The Math That Grows Money

Interest that earns interest โ€” the formula, the frequency gap, and why steady deposits and time do most of the work.

July 20, 2026 ยท 7 min read

How Many Rolls of Wallpaper Do I Need? Pattern Repeat Math

The wall-area takeoff, the usable yield of a roll, and why the pattern repeat decides your order.

July 20, 2026 ยท 6 min read

How Many Tiles Do I Need? Sizes, Waste & Boxes

The formula, the waste allowance that actually fits your layout, and how to turn a tile count into whole boxes.

July 20, 2026 ยท 7 min read

How Much Does Electricity Cost? Reading Your Bill in kWh

The kWh formula, the rate your bill actually charges, and what a heater, an always-on device, and standby power really cost.

July 20, 2026 ยท 6 min read

How Much Drywall Do I Need? Sheets, Mud & Screws

The area formula with the standard opening deductions, the sheet-size trade-off, and the mud, tape and screw counts that go with it.

July 20, 2026 ยท 6 min read

How Much Fencing Do I Need? Posts, Panels & Gates

One section count drives the whole bill of materials โ€” posts, panels, gates, and the concrete nobody tallies before the store run.

July 20, 2026 ยท 7 min read

How Much Flooring Do I Need? Boxes, Waste & Room Math

Floor area is the easy part. Waste tiers, box coverage, and rounding up are where the order goes wrong.

July 20, 2026 ยท 7 min read

How Much Grass Seed Do I Need? Rates by Grass Type

The rate for every grass type, the half rate for overseeding, and the seeding window that decides whether any of it works.

July 20, 2026 ยท 7 min read

What Is My BMR? Basal Metabolic Rate, Explained With Numbers

The Mifflin-St Jeor equation, what each input is worth, and why BMR is the floor of your calorie needs โ€” never the budget.

July 20, 2026 ยท 6 min read

What Size Air Conditioner Do I Need? BTU by Room Size

Floor area gives you the base number. Ceiling height, sun, bodies and a kitchen decide whether you buy that unit or the next one up.

July 20, 2026 ยท 7 min read

How Much Gravel Do I Need? Driveways, Paths & Drainage

The volume formula, the tons conversion, and the right depth and stone for every job.

June 20, 2026 ยท 7 min read

How Much Topsoil Do I Need? Lawns, Beds & Topdressing

The volume formula, the right depth for each job, and how topsoil differs from garden soil, compost, and fill dirt.

June 20, 2026 ยท 7 min read

How Much Concrete Do I Need? Slab Math, Bag Counts, and When to Call the Truck

Yards and bag counts for real projects โ€” patios, shed slabs, and deck piers โ€” with the ordering math nobody tells you.

June 20, 2026 ยท 6 min read