ToolSelf Blog
Guides on taxes, finance, business, and practical tools for freelancers and everyone.
College GPA vs High School GPA: How Admissions Compare Them
Most colleges recalculate your GPA to their own scale. Honors weighting at one school is not the same as another.
Sleep Cycle Calculator: Why 7.5 Hours Beats 8
Sleep happens in ~90-minute cycles. Waking at the end of a cycle (light sleep) feels great. Waking mid-cycle (deep sleep) feels terrible.
Self-Employment Tax: What You Owe & When
Self-employment tax is 15.3% — but most freelancers don't realize they can deduct half of it. Here's what you need to know.
Password-Protect a PDF: When and How
PDF passwords use AES-256 encryption by default. Pick a strong password — the encryption is only as good as the secret.
Currency Exchange Rates: How to Convert Money Internationally
Exchange rates fluctuate constantly. Here's how to understand rates and calculate real cost when dealing with international clients.
Contract Essentials: Protecting Yourself Legally
A simple contract protects both you and your client. Here's what to include: scope, payment terms, timeline, and IP rights.
MD5 vs SHA-1 vs SHA-256: Which Hash for Which Job
MD5 is broken for security. SHA-1 is deprecated. SHA-256 is the current default. Use the right algorithm for the right task.
Lifetime Value: How Much is Each Customer Worth?
LTV tells you the total profit from a customer over their entire relationship with you. Compare it to CAC to see if your business is sustainable.
Standard Deviation Explained Without Greek Letters
Standard deviation tells you how spread out your data is. Two datasets can share a mean and still look completely different.
Sales Tax: Do You Need to Collect It?
Sales tax rules vary by state and what you sell. Here's a simple guide to figuring out if you need to collect it.
Hex, RGB, HSL: A Color Format for Every Job
Hex is for handoffs. RGB is for math. HSL is for tweaking. Picking the right format speeds up every design task.
VAT for International Sellers: What You Need to Know
Selling to customers in the EU? VAT (Value Added Tax) rules apply. Here's what digital sellers need to know.