About the Blind Size Calculator
Blinds and shades are ordered by two numbers — width, then length (drop) — but the size you order is almost never the same as the size you measure. Manufacturers build in a small deduction for inside mount so the headrail clears the frame, and retailers recommend adding extra width and length for outside mount so the blind fully covers the opening. This calculator applies the standard sizing rule for whichever mount type you choose.
The formulas
Let W and H be your actual measured window width and height, in inches.
- Inside mount width: Order width = W − 0.5 in. The half-inch deduction gives the headrail and mounting brackets clearance so the blind can tilt and rotate without rubbing the sides of the frame.
- Inside mount length: Order length = H, with no deduction — order the exact height you measured from the top of the opening to the sill.
- Outside mount width: Order width = W + 2 × side overlap. The default overlap of 1.5 in per side (3 in total) is the commonly recommended minimum so the blind overlaps the frame edges and blocks light gaps when closed.
- Outside mount length: Order length = H + top/bottom allowance. The default of 3 in accounts for mounting the headrail above the top of the frame and letting the blind extend slightly below the sill.
How to measure
For inside mount, measure the width at the top, middle, and bottom of the opening and use the narrowest figure; measure the height at the left, center, and right and use the shortest figure — window openings are rarely perfectly square. For outside mount, measure the width and height of the area you want the blind to cover, since the deduction rule does not apply and you are choosing your own overlap instead. Round every measurement to the nearest 1/8 inch (0.125 in), which is the precision most blind manufacturers expect.
Reading the results
The calculator returns the order width and order length in inches (the numbers to enter on a blind manufacturer's order form), the same size converted to centimeters for reference, and the approximate area in square feet, which many retailers use as the basis for per-square-foot pricing.
Frequently Asked Questions
What is the difference between inside mount and outside mount?
Why do you subtract 1/2 inch from the width for inside mount?
How much extra width should I add for outside mount?
Should I measure to the nearest 1/8 inch?
Common Tip Percentages
| Service | Typical Tip Range | Notes |
|---|---|---|
| Restaurant (sit-down) | 15–20% | 20%+ for exceptional service |
| Food delivery | 10–20% | Consider extra for long distances |
| Taxi / rideshare | 10–20% | More for assistance with luggage |
| Hotel housekeeping | $2–5/night | Leave daily, not just at checkout |
| Barber / hair salon | 15–20% | On pre-discount total |
| Pizza delivery | 10–15% or $3–5 minimum | Higher in bad weather |
General Household Budget Ratios (50/30/20 Rule)
| Category | % of Net Income | Examples |
|---|---|---|
| Needs | 50% | Rent, groceries, utilities, insurance |
| Wants | 30% | Dining out, entertainment, hobbies |
| Savings / Debt | 20% | Emergency fund, retirement, extra payments |
Common Measurement Conversions for Everyday Use
| Quantity | US / Imperial | Metric Equivalent |
|---|---|---|
| 1 cup | 8 fl oz | 237 mL |
| 1 pint | 16 fl oz | 473 mL |
| 1 quart | 32 fl oz | 946 mL |
| 1 gallon | 128 fl oz | 3.785 L |
| 1 lb | 16 oz | 453.6 g |
| 1 ft | 12 in | 30.48 cm |