Why is self-employment tax calculated on 92.35% of my profit?

It mirrors the W-2 world, where the employer's half of payroll tax is not part of the employee's taxable wages. Multiplying by 92.35% removes the equivalent employer share before the 15.3% rate applies. It is one line in the formula, and it saves you real money, so do not skip it.

I made less than the standard deduction. Do I still owe taxes on 1099 income?

Very likely yes, and this is the most common nasty surprise at low incomes. The standard deduction only shields you from income tax. Self-employment tax is a separate calculation that starts at just $400 of net self-employment earnings and never touches the standard deduction. On $10,000 of net profit you would owe zero income tax and still owe roughly $1,413 of self-employment tax.

How does a W-2 job change this calculation?

Two ways. First, your side-hustle income stacks on top of your salary, so it starts getting taxed at your W-2 income's top bracket instead of climbing up from 10%; the chain in this article understates the income tax for W-2-plus-side-hustle situations. Second, Social Security coordinates: the SS wage base ($184,500 in 2026) counts your W-2 wages first, so high earners may owe only the Medicare portion of SE tax on side income. The mechanics of paying as you go are covered in the quarterly estimated taxes guide.

How to calculate your 1099 taxes by hand (the 6-step chain)

Q: Is the save 25-30% rule too much?

For a single filer with no other income, usually a little too much: the worked examples land at 18.6% effective at $40K and 20.5% at $70K, before state tax. But the rule survives because the errors it absorbs are all in one direction: state income tax, a W-2 job pushing your brackets up, or a better-than-expected quarter. Save 25-30%, and the worst case is you built a small buffer with your own money.

Bruce Samuels August 3, 2026 11 min read

Type "1099 tax calculator" into a search box, feed the same income into the first three results, and you will get three different answers with no explanation of why. That is not because the tax code is unknowable. It is because each calculator makes different silent assumptions, and you cannot see them. The threads asking for help all have the same shape:

“Can someone explain self employment taxes like I’m 5???”r/IRS, exactly as titled

Here is my attempt, and I have skin in this game: I got burned in my first side-hustle year precisely because the machine between "money I earned" and "tax I owe" was a black box to me. It turns out the machine is six steps long, you can learn it in twenty minutes, and once you own it, every calculator becomes checkable and every "how much should I set aside" question becomes arithmetic. I'm not a tax professional; I'm a guy who got burned and did a lot of homework. This is the homework.

Ground rules for this walkthrough: 2026 numbers, single filer, standard deduction, the side hustle is your only income, no dependents or credits, federal only. Every one of those assumptions is adjustable and I will flag where they bend, but you need the skeleton before you hang things on it.

The one idea that unlocks everything: you owe two different taxes

Nearly all 1099 confusion, including mine back then, comes from mashing two separate taxes into one mental bucket:

Self-employment tax (15.3%) is Social Security and Medicare. A W-2 employee pays half and their employer pays half, invisibly. You are both halves now. It applies from your first $400 of net profit and does not care about your standard deduction.
Federal income tax is the bracket system everyone knows. It does respect the standard deduction, and at side-hustle incomes it is usually the smaller of the two.

Two taxes, two calculations, one check to the IRS. Every step below feeds one or the other.

The 6-step chain

Step 1: Net profit, not gross receipts

Start with what you earned minus what it cost you to earn it: supplies, software, the business miles (72.5 cents for miles driven January through June 2026, 76 cents from July 1), the home office if you qualify, the business share of your phone. This is your Schedule C bottom line, and it is the number the whole chain runs on. Deductions are worth more than they look for exactly this reason: a dollar deducted here escapes both taxes.

For the worked example, say net profit is $40,000.

Step 2: Self-employment tax = net profit × 92.35% × 15.3%

The 92.35% multiplier exists to mirror the W-2 world, where the employer's half of payroll tax is not part of your taxable wages; you get the equivalent haircut before the rate applies.

$40,000 × 0.9235 = $36,940
$36,940 × 0.153  = $5,652   ← self-employment tax

One boundary: the Social Security portion (12.4 of the 15.3 points) stops at the 2026 wage base of $184,500. Below that, which is most of us, the flat formula holds.

Step 3: Deduct half of it to get your AGI

The IRS gives back a deduction for the "employer half" you just paid. Subtract half the SE tax from your profit:

$40,000 − $2,826 = $37,174   ← adjusted gross income (AGI)

Step 4: Subtract the standard deduction

2026 standard deduction, single: $16,100.

$37,174 − $16,100 = $21,074   ← taxable income, before one more deduction

Step 5: The QBI deduction, and the trap inside it

The qualified business income deduction gives most self-employed people 20% off, but 20% of what is where nearly everyone (including, at one point, an article on this site, which is why I harp on it) gets it wrong. It is the lesser of:

20% of your qualified business income ($37,174 × 20% = $7,435), or
20% of your taxable income from Step 4 ($21,074 × 20% = $4,215)

$21,074 − $4,215 = $16,859   ← final taxable income

At typical side-hustle incomes the taxable-income side is smaller, so if a calculator hands you the full 20%-of-profit version, it is quietly overstating your deduction and understating your tax. This single silent assumption explains a lot of the calculator disagreement from the intro.

Step 6: Run the brackets

2026 single-filer brackets: 10% up to $12,400; 12% from there to $50,400; 22% up to $105,700.

First $12,400 × 10%           = $1,240
($16,859 − $12,400) × 12%    = $535
Federal income tax             = $1,775

And the answer:

Self-employment tax   $5,652
Federal income tax    $1,775
Total federal         $7,427   (18.6% of the $40,000)

If you read our quarterly estimated taxes guide, that $7,427 should look familiar: it is the same example, because the chain is the same chain. There, it becomes four payments of $1,857; here, the point is that you can now produce it yourself.

Same chain at $70,000, compressed

To see how the machine scales, run it once more at a $70,000 net profit, this time at reading speed:

SE tax:     $70,000 × 0.9235 × 0.153        = $9,891
AGI:        $70,000 − $4,945                  = $65,055
Minus std:  $65,055 − $16,100                 = $48,955
QBI:        lesser of $13,011 / $9,791         = $9,791
Taxable:    $48,955 − $9,791                  = $39,164
Brackets:   $1,240 + ($39,164 − $12,400)×12% = $4,452
Total:      $9,891 + $4,452                    = $14,343   (20.5%)

One honest footnote before the observations: run this unrounded in the spreadsheet below and you get $14,342; rounding at each step, the way I just did on screen, lands $14,343. A dollar of drift from rounding order. Keep that in mind next time two calculators disagree by a few dollars: below about $20 of disagreement, you are usually looking at rounding conventions, not different tax law.

Two things worth noticing. The effective rate crept up only two points while income rose 75%, because SE tax is flat and the 12% bracket is wide. And SE tax is still two-thirds of the bill: at side-hustle incomes, Social Security and Medicare are the tax, and the income tax is the tip. That inversion is why W-2 intuition ("I barely owe anything at $40K") fails people so badly their first 1099 year.

The 6-cell spreadsheet

Here is the whole machine as formulas. Put your net profit in A1 and the rest is copy-paste:

A1:  your net profit (Schedule C bottom line)
B1:  =A1*0.9235*0.153                        SE tax
C1:  =A1-B1/2                                 AGI
D1:  =MAX(0, C1-16100)                        after standard deduction
E1:  =D1-MIN(0.2*C1, 0.2*D1)                  after QBI (lesser-of built in)
F1:  =IF(E1<=12400, E1*0.1,
      IF(E1<=50400, 1240+(E1-12400)*0.12,
      5800+(E1-50400)*0.22))                  federal income tax
G1:  =B1+F1                                   total federal tax
H1:  =G1/A1                                   your real effective rate

The F1 formula covers taxable income up to $105,700; if E1 lands past that, congratulations on the year you had, and also you have left the income range where a blog spreadsheet should be your tax plan. Update the constants each January (standard deduction, bracket edges, wage base) and this outlives every calculator tab you have ever closed.

Audit any calculator in three questions

Once you own the chain, you stop needing to trust calculators, and you can find a good one in thirty seconds by checking what it assumes:

Does it apply the lesser-of rule to QBI? Feed it a low income where the taxable-income cap should bind (our $40,000 case: correct QBI is $4,215, the naive answer is $7,435). If its tax comes out about $386 lighter than yours (the $3,220 of extra deduction times the 12% bracket), it took the naive 20%.
Does it deduct half the SE tax before income tax? Symptom: its AGI equals your gross profit. That mistake overstates tax; generous-looking calculators skip the QBI cap, lazy ones skip this deduction, and the two errors partially cancel, which is how two wrong calculators can agree with each other and not with the IRS.
Does it ask about W-2 income? If there is no field for it, the calculator is assuming your side hustle is your whole income, same as this article's skeleton. Fine for full-time freelancers, silently wrong for everyone moonlighting.

A calculator that passes all three is worth bookmarking. The spreadsheet passes by construction, because you built it.

The monthly habit that makes the number useless (in a good way)

Knowing your effective rate converts tax from a year-end ambush into a monthly transfer. My version, which has survived several years of real use: every month when I close the books, I multiply that month's net profit by my rate (rounded up to 25%), and move exactly that amount into a separate account that is not allowed to buy anything. Sub-accounts at Relay make this a two-minute job, but any second savings account works; the mechanism is the separation, not the bank.

The point of computing your real rate first is that the transfer stops feeling like a guess. At $40,000 of profit you know the skeleton says 18.6%; saving 25% means you also covered the state's slice and change. When the quarterly date comes around, the money is sitting there already labeled, and the payment is a chore instead of a crisis. That, more than any deduction trick, is the difference between people who dread January and people who do not.

What the skeleton leaves out, honestly

The recurring question this article exists to answer usually arrives with a situation attached:

“How much to set aside for 1099 taxes on side hustle?”r/tax

And the question is not new or platform-bound; the same thread has been running on Hacker News for a decade:

“Ask HN: Freelancers/Contractors, how do you deal with taxes?”Hacker News, title of the post

The chain answers it for the clean case. Here is what bends it, and in which direction:

A W-2 job bends it up, a lot. Side income stacks on top of salary, so it enters the brackets at your salary's altitude instead of climbing from 10%. The SE tax half of the chain barely changes; the income tax half can double or more. The quarterly guide works this exact case.
State income tax bends it up, unless you are lucky. I calculate from Texas, which takes nothing; if your state does, its rate goes on top of the effective rates above.
Married filing jointly bends it down (wider brackets, bigger standard deduction), dependents and credits bend it down further. Those are real returns, not skeleton territory.
Retirement contributions bend it down and are the one lever you control in December: a Solo 401(k) or SEP contribution reduces the income-tax side (not the SE side) while paying your future self.

So: compute your skeleton number, then round up toward 25-30% for the bends that apply to you. The rule of thumb survives not because it is precise but because its errors all point the same safe direction.

FAQ

Why is SE tax calculated on 92.35% of profit instead of all of it?

It strips out the employer-equivalent half of payroll tax before the 15.3% applies, the same way W-2 wages exclude the employer share.

I made less than the standard deduction. Do I still owe?

Very likely yes, and this is the classic low-income surprise (the version of it that shows up as "making less than the standardized deduction, how to calculate?" on r/tax). The standard deduction only shields income tax; SE tax starts at $400 of net profit and ignores it entirely. On $10,000 of net profit: income tax $0, SE tax about $1,413. The chain handles this automatically, which is what the MAX(0, ...) in cell D1 is doing.

How does a W-2 job change the math?

Your side income enters the brackets at your salary's altitude (income tax up), and the Social Security wage base counts your W-2 wages first, so high earners may owe only the Medicare portion of SE tax on side income. Both effects are covered with a worked example in the quarterly guide.

Is the "save 25-30%" rule too much?

For the clean single-filer case, a little: the examples land at 18.6% and 20.5% federal. The rule survives because everything it absorbs (state tax, a W-2 job, a good quarter) pushes in the same direction. Worst case, you tipped your savings account.

Where to go next: turn the annual number into four payment dates with the quarterly estimated taxes guide, shrink the Step 1 number legally with the deductions guide, or read the anatomy of a first-year tax shock if this article found you after the bill arrived.