Construction calculators

Rmc Calculator

Updated Sep 7, 2026 By Jehan Wadia
Rate Formulas

Structure Type

Dimensions — set a unit on each field

Concrete Volume — Slab

Ready mix concrete required:

0.00 cu yd
cubic yards — the standard ordering unit for ready mix concrete
Cubic Feet
0.00 cu ft
Cubic Meters
0.00 m³
Estimated 60 lb bags
0
Estimated 80 lb bags
0
Order QuantityCubic YardsCubic FeetCubic Meters
Step-by-Step Solution
Order Volume With Waste Allowance

Introduction

RMC means two different things, so this tool does both. Pick the mode you need at the top.

Concrete RMC stands for Ready Mix Concrete. Use this mode to find out how much concrete to order. Enter your sizes for a slab, square footing, trapezoidal footing, beam, square column, or circular column. You can type in inches, feet, or meters. The tool gives you the volume in cubic yards, cubic feet, and cubic meters. It also counts 60 lb and 80 lb bags for small jobs, and adds a 5% to 10% waste allowance so you do not come up short on pour day.

Military Pay RMC stands for Regular Military Compensation. Use this mode to see what your military pay is worth as a civilian salary. Enter your monthly base pay, BAH, and BAS, then pick your filing status. BAH and BAS are not taxed, so they are worth more than they look. The tool adds that tax advantage and shows the civilian salary you would need to match your pay.

Both modes show the step-by-step math and a chart, so you can check the numbers yourself.

How to use our RMC Calculator

Our RMC Calculator works in two ways. Pick Military Pay RMC to turn your military pay and allowances into a civilian salary number, or pick Concrete RMC to find how much ready mix concrete you need. Fill in the boxes below, and the tool gives you your total, a step-by-step math breakdown, and a chart.

Military Pay RMC inputs

Service Member Type: Choose Enlisted or Officer. This sets your default BAS rate.

Monthly Base Pay ($): Type your taxable base pay for one month, from your pay chart or LES.

Monthly BAH ($): Type your Basic Allowance for Housing for one month. This money is not taxed.

Monthly BAS ($): Type your Basic Allowance for Subsistence for one month. This money is not taxed either.

Federal Tax Filing Status: Pick Single or Married Filing Jointly. This sets your standard deduction and tax rate.

Click Calculate RMC to see your civilian equivalent salary, total cash pay, and tax advantage.

Concrete RMC inputs

Structure Type: Pick the shape you are pouring: Slab, Square Footing, Trapezoidal Footing, Beam, Square Column, or Circular Column.

Length: Enter how long the pour is, then pick inches, feet, or meters.

Width: Enter how wide the pour is, then pick your unit.

Thickness, Depth, or Height: Enter how deep or tall the pour is, then pick your unit. Slab thickness is often 4 inches.

Diameter (Circular Column): Enter the width of the round column across the middle, then pick your unit.

Base Length, Base Width, and Base Height (Trapezoidal Footing): Enter the size of the flat bottom slab.

Vertical Slant Height (Trapezoidal Footing): Enter the height of the sloped part above the base slab.

Pillar Length and Pillar Width (Trapezoidal Footing): Enter the size of the small top of the taper where the column sits.

Click Calculate Volume to get your concrete in cubic yards, cubic feet, and cubic meters, plus bag counts and a 5% to 10% waste allowance for your order.

What Does RMC Mean?

RMC stands for two very different things. In construction, RMC means Ready Mix Concrete. In the military, RMC means Regular Military Compensation. This tool covers both, so pick the mode you need.

Ready Mix Concrete (RMC)

Ready mix concrete is concrete that is mixed at a plant and trucked to your job site in a rotating drum. It shows up wet and ready to pour. Because a plant mixes it by weight with tight controls, the strength and slump stay steady from load to load. That is why almost every slab, footing, beam, and column bigger than a small repair is poured with ready mix.

Ready mix is sold by the cubic yard. One cubic yard equals 27 cubic feet, or about 0.765 cubic meters. A cubic yard of concrete weighs close to 4,000 pounds. Most trucks hold 8 to 10 cubic yards, and most plants have a minimum order of about 1 cubic yard plus a short-load fee if you order less.

How Concrete Volume Is Found

Volume is just the space the concrete will fill. Every dimension must be changed to the same unit first, then multiplied:

  • Slab, footing, beam, square column: length × width × thickness (or height)
  • Circular column: π × radius² × height
  • Trapezoidal footing: the flat base slab volume plus the sloped top part, found with the frustum rule ⅓ × height × (A₁ + A₂ + √(A₁ × A₂))

Divide the answer in cubic feet by 27 to get cubic yards.

Why You Order Extra

Always order 5% to 10% more than the exact number. Forms bulge, subgrade dips, some mud sticks in the chute, and a little spills. Running short is far worse than having a bit left over, because a second truck costs more and the cold joint between two pours is a weak spot.

Bagged mix is only for small jobs. A 60 lb bag yields about 0.45 cubic feet and an 80 lb bag yields about 0.60 cubic feet. It takes roughly 45 to 60 bags to make one cubic yard, so anything past half a yard is usually cheaper and easier as ready mix.

Common Thickness Guides

  • Sidewalks and patios: 4 inches
  • Driveways for cars: 4 to 5 inches
  • Driveways for trucks or RVs: 5 to 6 inches
  • Garage and shed floors: 4 to 6 inches

Regular Military Compensation (RMC)

Regular Military Compensation is the Department of Defense way of showing what a service member really earns. It adds up four parts:

  • Basic Pay: the taxable monthly paycheck, set by rank and years of service
  • BAH: Basic Allowance for Housing, tax free
  • BAS: Basic Allowance for Subsistence (food money), tax free
  • Tax Advantage: the federal tax you would have paid on BAH and BAS if they were taxed

BAH and BAS never show up on a W-2, so a plain look at base pay makes military pay seem low. The tax advantage fixes that. It equals your yearly allowances times your marginal federal tax rate. Add it to your total cash pay and you get the gross civilian salary you would need to take home the same money.

RMC does not include special pays, bonuses, hazard pay, health care, or the pension. Those add even more value on top.


Formulas used

Civilian Equivalent Annual Salary (RMC)
\text{RMC}_{\text{civ}} = \text{Annual Cash Pay} + \text{Tax Advantage}
Annual Cash Pay
\text{Annual Cash Pay} = (\text{Base Pay}_{\text{mo}} + \text{BAH}_{\text{mo}} + \text{BAS}_{\text{mo}}) \times 12
Taxable Income and Tax Advantage
\text{Taxable} = \max\left(0,\; \text{Base Pay}_{\text{mo}} \times 12 - \text{Standard Deduction}\right),\quad \text{Tax Advantage} = (\text{BAH}_{\text{mo}} + \text{BAS}_{\text{mo}}) \times 12 \times \tau
Rectangular volume (slab, square footing, beam, square column)
V = L \times W \times H
Circular column volume
V = \pi \times \left(\frac{d}{2}\right)^2 \times h
Trapezoidal footing volume
V = A_{1} \times h_{b} + \frac{1}{3} h_{s} \left(A_{1} + A_{2} + \sqrt{A_{1} A_{2}}\right),\quad A_{1} = L_{b} W_{b},\; A_{2} = L_{p} W_{p}
Volume unit conversions
V_{\text{yd}^3} = \frac{V_{\text{ft}^3}}{27}, \qquad V_{\text{m}^3} = V_{\text{ft}^3} \times 0.028316846592
Pre-mix bag count and waste allowance
N_{60} = \left\lceil \frac{V_{\text{ft}^3}}{0.45} \right\rceil,\quad N_{80} = \left\lceil \frac{V_{\text{ft}^3}}{0.60} \right\rceil,\quad V_{\text{order}} = V \times (1.05 \text{ to } 1.10)

Frequently asked questions

How long can ready mix concrete stay in the truck before it is poured?

About 90 minutes from the time water hits the cement at the plant, or 300 drum turns, whichever comes first. That is the industry rule under ASTM C94.

Hot, dry, or windy days shorten that window. Have your forms, tools, and crew ready before the truck rolls up so the load pours without waiting.

How many square feet does one cubic yard of concrete cover?

One cubic yard is 27 cubic feet, so coverage depends on how thick you pour:

  • 4 inches thick: about 81 square feet
  • 5 inches thick: about 65 square feet
  • 6 inches thick: about 54 square feet
  • 8 inches thick: about 40 square feet

These numbers are exact math with no waste added. Add 5% to 10% for a real order.

How much concrete do I need for a 10 by 10 slab that is 4 inches thick?

10 ft × 10 ft × 0.333 ft = 33.3 cubic feet, which is 1.23 cubic yards.

Order about 1.3 to 1.4 cubic yards so you have a little extra. Most plants have a 1 yard minimum, so this pour is a fine ready mix order.

What is the difference between cement and concrete?

Cement is the gray powder that acts like glue. Concrete is the finished material: cement plus sand, gravel, and water.

You never pour plain cement. Ordering "a truck of cement" really means a truck of concrete.

What is concrete slump and what slump should I order?

Slump measures how wet and runny the mix is. A cone of fresh concrete is turned over, and how far it sags in inches is the slump.

  • 3 to 4 inches: footings and driveways
  • 4 to 5 inches: most slabs and patios
  • 5 to 7 inches: walls and tight forms with lots of rebar

Higher slump is easier to place but weaker if it came from adding plain water.

Can the driver add water to the concrete at my job site?

A small amount is allowed only if the mix has held back some of its design water. After that, stop.

Every extra gallon of water per cubic yard can cut strength by roughly 200 to 300 psi and cause cracks and dusting. If the mix is too stiff, ask the plant for a water reducer or plasticizer instead.

What is a short load fee for ready mix concrete?

It is an extra charge when you order less than a full truck. Most plants set a minimum of about 8 to 10 cubic yards and charge a fee per yard you fall short.

Short load fees often run $40 to $80 per missing yard. For pours under 1 cubic yard, bagged mix is usually cheaper.

How long before you can walk or drive on new concrete?

  • Walk on it: 24 to 48 hours
  • Drive a car on it: about 7 days
  • Heavy trucks or RVs: 28 days

Concrete reaches roughly 70% of its strength in 7 days and full design strength at 28 days. Keep it damp the first week so it cures strong.

What does a concrete strength like 3000 psi or M20 mean?

It is the crushing strength the mix should reach in 28 days.

  • 2500 psi: light work, small pads
  • 3000 to 3500 psi: patios, sidewalks, most home slabs
  • 4000 psi and up: driveways, garage floors, footings that carry heavy loads

M20 is the metric version. It means 20 MPa, or about 2,900 psi.

How deep should a concrete footing be?

Footings must sit below the local frost line so the ground cannot heave them. That is 12 inches in warm states and 42 to 48 inches in cold ones.

A common house footing is 12 inches thick and at least twice as wide as the wall it holds. Always check your local building code first.

Do I need rebar or wire mesh in a concrete slab?

Yes for anything that carries weight. Concrete is strong when squeezed but weak when pulled, and steel fixes that.

  • Patios and sidewalks: wire mesh or fiber mix is usually enough
  • Driveways and garage floors: #3 or #4 rebar in an 18 inch grid

Keep the steel in the middle of the slab, not lying on the dirt.

Is BAH taxed?

No. Both BAH (housing) and BAS (food) are free of federal and state income tax, and they are not on your W-2.

That is why $1,800 of BAH is worth more than $1,800 of base pay. Regular Military Compensation adds that tax break back in so you can compare your pay to a civilian salary.

Do you get BAH if you live in the barracks or on base housing?

Usually no. Single members in the barracks do not receive BAH because housing is provided.

Families in on-base housing are paid BAH on paper, but it goes straight to the housing office. You only keep BAH when you rent or buy off base.

Do lenders count BAH and BAS when I apply for a mortgage?

Yes. Most lenders count them as income and many gross them up by 15% to 25% because the money is tax free.

So $2,000 of monthly BAH can count like $2,300 to $2,500 of regular pay. Bring your LES to show the amounts.

What is a marginal tax rate?

It is the tax rate on your last dollar earned, not on all your money.

If you are in the 22% bracket, only the income above that bracket line is taxed at 22%. The dollars below it are still taxed at 10% and 12%. Regular Military Compensation uses your marginal rate to value your tax free allowances.

How does Regular Military Compensation compare to civilian pay?

The Department of Defense aims to keep RMC near the 70th percentile of pay for civilians with similar age and education.

RMC leaves out health care, the pension, special pays, and bonuses, so real total value is higher than the RMC number alone.