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Every formula. Every source. No black boxes. Most calculators just give you a number. We show you exactly how we got there.
Try a ShowMath Calculator→The problem
Every other calculator is a black box.
You put numbers in, a number comes out. You have no idea if it's right, outdated, or using your state's actual rules.
When it's your taxes — that matters. The difference between a correct and incorrect quarterly estimate can mean a penalty, an audit flag, or leaving thousands on the table.
You deserve to see the work.
How it works
Every step. Every formula. Every source.
Here's an actual ShowMath panel from the Self-Employment Tax calculator. This is exactly what you see when you click “Show the math.”
Step 1 — SE Tax Base
seBase = netProfit × 0.9235
$80,000 × 0.9235
= $73,880
You pay SE tax on 92.35% of net profit, not the full amount. The 7.65% reduction represents the employer-equivalent half of FICA that W-2 employees don't see — it's taken before the tax is applied.
IRC §1401; IRS Schedule SE (Form 1040)
Step 2 — SE Tax (Self-Employment Tax)
seTax = seBase × 0.153
$73,880 × 15.3%
= $11,304
15.3% covers Social Security (12.4%) + Medicare (2.9%). As self-employed, you pay both the employee and employer halves — but you get a deduction for the employer half.
IRC §1401(a), §1401(b); Social Security Act §3101
Step 3 — SE Tax Deduction (above-the-line)
seDeduction = seTax × 0.5
$11,304 × 50%
= $5,652
You deduct half the SE tax from gross income before calculating income tax. This mirrors how employers deduct their FICA contributions — so self-employed workers get the same tax treatment.
IRC §164(f)
Key insight
On $80,000 net profit: SE tax is $11,304, but the deduction saves ~$1,695 in income tax (at 30% combined rate). True SE tax burden: ~$9,609 — or 12.0% of gross.
#ShowYourWork
Try the full calculator →The standard
ShowMath isn't just a feature. It's a standard.
Every calculator on reise-tools is built to this standard: real math, real sources, real answers.
Transparent
Every calculation step is visible. You see the formula before the numbers, the numbers before the result.
Cited
IRC sections, IRS publications, SSA rules. If we used it, we cite it. You can verify every number we use.
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