Calculation is client-side, income figures are never transmitted or stored.
How Washington Child Support Is Calculated
- Determine each parent's monthly net income, then combine both for combined monthly net income.
- Look up the basic child support obligation from the official Economic Table for combined income and number of children (table covers 1-5 children; 6+ uses the 5-child figure).
- Each parent's share equals their income divided by combined income, applied to the basic obligation.
- A presumptive minimum of $50/child/month applies whenever the paying parent's net income is below the Self-Support Reserve (180% of the one-person federal poverty guideline, $2,394/month as of the 2026 guidelines).
- Above that minimum, the basic obligation may not reduce the paying parent's net income below the Self-Support Reserve.
- Total support owed for ALL of that parent's children (not just this case) is capped at 45% of net income.
- Above $50,000/month combined net income, courts may exceed the presumptive amount only upon written findings of fact.
Washington Child Support Worksheet Walkthrough
Example: combined net income $8,500/month, 2 children, Parent A earns $5,000/mo (59% share), Parent B earns $3,500/mo (41% share, above the $2,394 Self-Support Reserve) and is the noncustodial parent.
- Basic child support obligation for $8,500 combined, 2 children: $993.50/month.
- Parent B's share: 41.18% × $993.50 ≈ $409/month — above both the $100/month minimum (2 × $50) and the Self-Support Reserve floor, so the standard prorated amount applies.
How This Calculator Works — Formula & Constants
Source: Revised Code of Washington § 26.19.020 (Washington State Legislature) · Calcul déterministe — no AI, no arbitrary estimate.
Constants used
| Constant | Value | Source |
|---|
Formula
base_obligation = schedule_lookup(combined_income, children)
share_B = parentB_income / combined_income
total_obligation = base_obligation + childcare_cost + health_insurance_cost
obligation_B = total_obligation × share_B
Deterministic calculation based on Washington's official guideline schedule table. Verify against Washington's official calculator for a court-ready figure.
FAQ
How is child support calculated in Washington?
Determine each parent's monthly net income, then combine both for combined monthly net income. Look up the basic child support obligation from the official Economic Table for combined income and number of children (table covers 1-5 children; 6+ uses the 5-child figure). Each parent's share equals their income divided by combined income, applied to the basic obligation. A presumptive minimum of $50/child/month applies whenever the paying parent's net income is below the Self-Support Reserve (180% of the one-person federal poverty guideline, $2,394/month as of the 2026 guidelines). Above that minimum, the basic obligation may not reduce the paying parent's net income below the Self-Support Reserve. Total support owed for ALL of that parent's children (not just this case) is capped at 45% of net income. Above $50,000/month combined net income, courts may exceed the presumptive amount only upon written findings of fact.
What is Washington's Self-Support Reserve and how does it work?
The Self-Support Reserve (SSR) is 180% of the federal poverty guideline for a one-person household — $2,394/month as of the 2026 guidelines. The basic child support obligation generally may not reduce the paying parent's net income below this amount. However, a presumptive minimum of $50/child/month always applies, even if that would dip into the reserve, unless the obligor shows it would be unjust.
Is there a cap on how much child support Washington can order?
Yes — total support a parent owes for ALL of their biological or legal children (not just the children in a specific case) cannot exceed 45% of that parent's net income, except for good cause shown (such as substantial wealth or special medical/educational needs). This calculator applies the cap to the case at hand but can't account for a parent's other support obligations outside it.
What happens if combined income is above $50,000/month in Washington?
Above $50,000/month in combined net income, Washington's Economic Table doesn't extend further — courts may exceed the presumptive amount set at $50,000 only upon written findings of fact, not automatically. This threshold itself was unchanged by the 2026 update; what changed was the LOWER threshold, which rose from $1,000 to $2,200/month.
Does Washington's schedule cover 6 or more children?
No — Washington's official Economic Table (RCW 26.19.020) only has columns for one through five children, unlike most other states' schedules which extend to six. For six or more children, this calculator uses the five-child figure as an approximation, since the statute itself doesn't define a specific amount beyond five.
Methodology & Source
Formula model: income shares. Effective 2026-01-01, guideline version 2026-WA-v1, last reviewed 2026-07-12.
Official source: Revised Code of Washington § 26.19.020 (Washington State Legislature) (RCW 26.19.020, RCW 26.19.065).
Above $50,000/month combined net income, Washington's economic table has no further table value — courts may exceed the $50,000 presumptive amount only upon written findings of fact. This calculator does not model the 45% cap across a parent's OTHER children outside this case, or deviations for residential time under RCW 26.19.075.
Guideline figures transcribed from the primary source above and cross-checked against Washington's official calculator/worksheet for multiple test scenarios — see our verification methodology.